Lost Technology

""I have said this before, and I do feel it is worth reiterating for those of you about to embark on archaeology degrees: ancient and powerful civilizations do NOT leave dangerous weapons lying around on the off chance that their descendants might someday find themselves in a tight squeeze and need them.""

- Professor Bernice Summerfield, "Beyond the Sun"

""To be fair, we don't invent them. We find them. They're gifts, Mr. Miles, from Those Who Came Before.""

- Warren Vidic, Assassin's Creed

Beyond Schizo-Tech, beyond Scavenger World, there's Lost Technology.

Applied Phlebotinum. Similar to Imported Alien Phlebotinum, with the catch that the current population comprises the survivors or replacements of an age that fell due to its arrogance, war, or some other catastrophe.

Let's face it. The Ancients had some pretty neat gear. Robots, weapons, even the answer to The Ultimate Question of Life, The Universe, and Everything. Easy to use, little or no maintenance required, and after thousands of years of neglect often still in perfect working order!

...oh yeah, and this technology completely and utterly destroyed the Ancients and most of the world with it. But that doesn't stop the villains (or the heroes) from wanting to get some for themselves by pillaging an Advanced Ancient Acropolis. Usually, said Lost Technology then tries to destroy the world again. Some, but not all, heroes are smart enough to try to keep people away from the stuff.

Occasionally the good guys need Lost Technology to combat ancient evils that have arisen again (or villains who have acquired Lost Technology of their own). They usually use it as best they can, despite Black Boxes. Still, they suffer from Low Culture, High Tech. Often, this is the origin of a Superhero, and it can justify why the Disposable Superhero Maker won't work twice.

May also show up in the guise of Lost Magic in fantasy settings. Often a consequence of No Plans, No Prototype, No Backup. Also see Sufficiently Advanced and Pointless Doomsday Device. Compare Bamboo Technology. A subtrope of Older Is Better. Frequently overlaps with Sufficiently Advanced Bamboo Technology.

Anime and Manga

 * In Mazinger Z, the plot is set in motion when Big Bad Dr. Hell finds an army of giant robots in the underground mazes of the Greek island his archaeological expedition was researching, belonging to the lost Mykene civilization. Instantly he decides seizing that technology to furthering his goals. Too bad to him -and the world- the legitimate owners of that technology were still around (like it was seen in Great Mazinger)...
 * In one of the UFO Robo Grendizer mangas, Lost Technology had an important -and dire- role.
 * In Kotetsu Jeeg, Dr. Shiba finds several ancient mysterious magical artifacts and hieroglyphs during an archaeological expedition. His findings provide evidence of the ancient lost kingdom of Yamatai that thrived in south of Japan has survived, and its Queen Himika is preparing to invade Japan. Of course, his reaction was using that lost technology to get a countermeasure ready (i. e., turning his eldest son into a cyborg capable transforming into a Humongous Mecha).
 * In The Mysterious Cities of Gold, the little bits of surviving technology from the Mu Empire are this, including a solar powered warship that shoots lasers, a solid gold airplane, and . Fighting against Spanish galleons and Mayincatecs with spears.
 * The City in Blame is so immeasurably vast that "lost" technology is positively ubiquitous, which isn't surprising, considering that the mega structure was built over the span of thousands of years and encompasses most of the solar system. For a more obvious example, Killy's weapon is revealed to be an ancient and legendary piece of technology that nobody has been able to replicate. He is mildly shocked to learn this.
 * Keeping people from (while recklessly getting into) the stuff is a major premise of Galaxy Angel, which is called Lost Technology in the series. The serious Galaxy Angel gameverse has it in droves, but replace backtalking missiles with, say, dangerous ones.
 * The Demon God Androids, the Eye of God "Death Star", the Trigger of Destruction battleship, etc. etc. from El-Hazard: The Magnificent World.
 * Mai-Otome
 * Magical Girl Lyrical Nanoha has a ton of this stuff, and it's always a major part of whatever crisis the main characters are facing. Magic was specifically nurtured and developed in order to handle the multiple times someone finds a "Lost Logia" and accidentally (or intentionally) pushes the "destroy planet" button.
 * Showed up often in Bakuretsu Hunters.
 * The demi-armors from Maze Megaburst Space.
 * The eponymous airships in Simoun are so far lost that their origin isn't clearly remembered.
 * Texhnolyze
 * Technically the technology is only lost to the population of Lukuss - the Class and the Theonormals never lost it.
 * The doll Emily in Soukou no Strain turns out to be Lost Technology... with dubious origins.
 * An ancient war machine forms a important part of the plot of Nausicaa of the Valley of the Wind.
 * Due to citywide amnesia, the megadeuses from The Big O are Lost Technology despite being little more than 40 years old.
 * Boson Jump and Phase Transition technology in Martian Successor Nadesico.
 * In Murder Princess, the Lost Technology is actually called Lost Technology, proper noun.
 * This is the whole basis of the manga 666 Satan (aka 666 Satan) with
 * Trinity Blood. Not only is it actually called Lost Technology but they even heavily analogize Lost Technology to magic by giving it mystical references.
 * The technology of Laputa in Laputa: Castle in the Sky. Unusually, it did not destroy them; they voluntarily threw it away because it was alienating them from the earth.
 * The main theme of Turn a Gundam. To fight back against the alien humans of the Moon Race, Earth (which appears to have somehow gone back to the Victorian era) starts digging up old mobile suits and battleships it finds. Turns out
 * Also used as the plot for the more kid aimed spin off Musha Generation, alabeit with the mecha now super deformed, more fantasy elements to the cast and the overall theme being the way of the samurai.
 * In Trigun they literally call the Plants ("Lost Technology.") The Plants are like power plants, they produce energy that allows humans to survive on the planet Gunsmoke. The Plants were invented on another, now mostly mythical planet (Earth), and with one exception the knowledge of how and why the Plants work is completely forgotten.
 * Gun X Sword is a Spiritual Successor to Trigun and also uses this. Two examples are the feuding sisters  and that cross puzzle Van tries to open which turns out to be an electromagnetic shield for his mecha.
 * Lost Universe with its Lost Ships and Psi Weapons. Depending on the Fanon accepted the Lost Technology may Gods and Demons in the form of technology.
 * In Break Blade, the hero Rygart's mecha or err Golem is not made of quartz like everyone else's, oh no his is an unholy fusion of cheap metal, oil and he is apparently the only one who can use it viceversa goes for the quartz golems. Besides being this trope it is also faster and stronger than anything made from quartz.
 * In So Ra No Wo To only 10 Tamekicaduchis are left, and it takes a Teen Genius to make one operational.
 * In Fairy Tail, "Lost Magic" is, according to Master Hades of Grimoire Heart, the magic closest to the source of all magic in their world . The strongest members of his guild, the Seven Kin of Purgatory, are armed with Lost Magic and are extremely powerful.
 * In Heat Guy J, humanity has gone several steps back technology wise, after a calamitous war. The most advance technology is being controlled and maintained by an apparently benevolent group known as the Celestials. In fact a number of laws were enacted after the war to prevent humans from regaining some of the more destructive technologies, notability research into android has been outlawed (with some exceptions) and the only android allowed within city limits or populated areas is J.
 * Lost Technology is both the central MacGuffin and the enabling device in Spriggan, which revolves around an archeological arms race between cold war powers, a few secretive fringe groups, and the ARCAM foundation, which seeks to secure (or if that's not possible, disable beyond repair or useful R&D) all "Out-of-Place Artifacts", or "OOPArts", until such time as they feel that the rest of humanity is ready to use them responsibly.
 * Warp technology in Diebuster was purposefully suppressed after humanity gave up trying to explore the galaxy thousands of years ago, to the point that nobody even knows the first principles behind it. And then, of course, there's.

Literature

 * In JRR Tolkien's universe, older technology is always superior to newer technology, since the original crafts and techniques were largely perfect and Tolkien's universe's history is essentially a process of forgetting (losing) those crafts and techniques, not discovering better ones.
 * The Silmarillion states that the people of the First Age built an elven ship made of "mithril and elven-glass" that could travel both through the sky and through the Outer Void(outer space). When Morgoth destroyed Gondolin, the great Elven city hidden in the mountains, he crossed the peaks with metal troop carriers that had fire in their bellies(i.e. engines). In the Second Age, the Númenóreans are said to have had ships that moved against the wind, with weapons that could "fire darts across an ocean." One version of the legends says that the Númenóreans in exile even managed to build aircraft in a futile attempt to escape the newly round world.
 * In Asimov's Foundation novels, most of the galaxy loses its tech when the Empire collapses; the Foundation preserves, improves and reintroduces it. In the later novels,  are a lost technology universally believed to be mythological, until the heroes meet the last surviving one in the final pages of the last book.
 * Much of the phlebotinium in the Mortal Engines series comes in the form of lost technology.
 * Terry Pratchett's Discworld novel Thud! introduced Lost Technology in the form of "Devices", mysterious magical/technological devices found and utilized by the dwarfs. Two examples are a cube that functions as an early audio recording device, and something which is described as simply two blocks with some sort of bearing between that causes them to rotate in opposite directions. Forever and no matter how strong a force is used to try and hold them. Basically an infinite mechanical engine that can power anything on nothing.
 * Lost technology and the ruins of long lost high-tech civilizations turn up in the Dying Earth novels (and the fantasy RPG) by Jack Vance, as well as in several of his other short stories (both fantasy and science fiction).
 * There are hints of a previous, lost technological civilization in some of the Shannara novels, a fantasy series by author Terry Brooks. In Sword of Shanarra, the characters are told the civilisation destroyed itself with powerful weapons, and encounter a mutant-cyborg monstrosity in a ruined city. This aspect is not played up so much in the later novels, although the Big Bad in one is an AI from the old world.
 * Brooks is currently linking this to his Urban Fantasy series World/Void: the Genesis of Shanarra series is set After the End of World/Void.
 * The "Genesis of Shannara" series openly reveals that
 * Robert Jordan's Wheel of Time series heavily plays the Lost Magic angle up, stocking the world full of unknown thousand-year-old devices mostly in working order, sometimes harnessed and sometimes just accidentally triggered. The Hero is given glimpses into the pre-cataclysm world, as well. At one point, the reader is afforded a glance at a "three-pointed star in a circle, older than all the other objects, reeking of pride and vanity". Or, as we call it today, the Mercedes-Benz logo.
 * The "Age of Legends" was pretty much a personification of a Crystal Spires and Togas world, complete with
 * Along with the fairly obvious Mercedes-Benz logo, there's mention of the giants "Merck" and "Mosk" who fought with fire-tipped lances, "Lenn" who rode an "eagle" to the Moon, and the great queen "Elsbeth". Since the "Age of Legends" is the Second Age of the World (and Jordan has mentioned that there are Ages when nobody knows of the One Power), this has spawned speculation that our current Age is the First Age, preceding the Age of Legends.
 * Valyrian steel in A Song of Ice and Fire, and though not really technology, in some weird manner, dragons.
 * Valyrian steel is a fantasy counterpart to a real-world "lost" technology: Damascus steel.
 * Also, the techniques used to raise the Wall, a seven-hundred foot tall wall of ice spanning a continent, built eight thousand years before the series takes place.
 * In Stephen King's The Dark Tower Series, Roland's world is littered with remnants of the super-advanced technology of the "Great Old Ones", including artificial intelligence, robots, and advanced weaponry. Elements of this technology frequently become central drivers of the plot.
 * Lost Technology - Lost Magic version in the Deryni works:
 * Deryni went from having thriving Healer schools and a regular cadre of Healers as part of society to no Healers in the whole of Gwynedd, with a very slight comeback (a handful of untrained Healers flying by the seat of their pants) two centuries later. Arcane knowledge generally is hidden away and /or lost, with traces gradually coming to light.
 * Camber and his family circle also investigate more ancient ancestors Orin and Jodotha, as well as a strange altar with black and white cubes (akin to Wards Major) showing patterns they've never seen, much less used. Testing shows one of the patterns makes the altar drop into the floor to reveal a secret room beneath it.
 * In Second Apocalypse, there is the Tekne, the highly advanced technology of the alien Inchoroi race (including beam weapons and highly capable, sophisticated genetic engineering). The remnants of the Inchoroi are largely ignorant of how their technology works, and use it in a black box, "trial-and-error" fashion.
 * An ancient galaxy-spanning Internet exists in Vernor Vinge's A Fire Upon The Deep, with all the associated dangers such as viruses, translation errors, and propaganda. The novel is about what happens when a malevolent power, the Straumli Perversion, is released from one of these archives by a team of archaeologist programmers.
 * The stagnant remnants of a world spanning autocracy that has frozen it's culture for tens of thousands of years meets it's comeuppance in the form of a one way time traveller and his knowledge in another Vinge story, "The Peddler's Apprentice". His list of tricks consists of a self defense gadget, and the uplink codes to the array of spy and killsats left behind by Sharn, the "crystal city" the Kingdom of Fyffe devolved from.
 * In a Star Trek: Deep Space Nine novel, the crew of the Defiant runs across a world that was essentially SET UP this way as an experiment. A highly-advanced culture dropped off a whole bunch of their babies on a planet with tons of small, hi-tech devices scattered all over the place and sat back to see what would happen. We then get the people who are so dependent on technology they don't understand that they're royally screwed when the batteries go dead.
 * In Ayn Rand's Anthem Lost tech includes a subway system and an abandoned house.
 * The series The General, by David Drake and S.M. Stirling (later, Eric Flint steps in for Stirling), has a Lost Technology computer providing information for a planet at a development stage akin to the American Civil War on Earth, to eventually rebuild interstellar travel over a millennium after it was lost due to a galactic civil war.
 * The titular quest in Hiero's Journey is about a search for lost computer technology in an After the End world.
 * T. E. Bass' Half Past Human depicts an Earth about 3000 years in our future, where humans have devolved into a four-toed variety (called the Nebish) and technology appears to have declined as well (although it's still higher than ours). There are two instances of Lost Technology in this novel, both owned by (and planted to assist) the few remaining five-toed outcasts; one gets dismantled by Nebish technicians, who fail to recognise it as a Class 6 cybernetic device, since it's small and portable and their understanding of Class 6 cybers is that the brain case alone would weigh over two tons.
 * The city of Diaspar in Arthur Clarke's The City and the Stars (a novel-length re-working of his earlier novella Against the Fall of Night) is composed of technology that no one living understands any longer; but which is all fully automated and self-repairing. Somewhat subverted in that the computer that maintains the city, including the inhabitants—who are cloned reincarnations of the original population with memories of all their incarnations stored in the computer—could conceivably produce new inhabitants with the requisite memories. The technology necessary for space travel, on the other hand, had been deliberately purged both from the city computer's memory, and the records of the telepathic inhabitants of the pastoral city of Lys; and the populations of both cities had developed a phobia of space travel, with a powerful  mythology justifying their fear.
 * In the Warhammer 40,000 novel Dark Adeptus,  is able to be Not Quite Dead thanks to some hitherto-unknown tech he finds shortly before he gets killed. The   is also shown to be comprised of tech that its copiers cannot replicate fully.
 * Larry Niven's Ringworld and everything on it.
 * The technology of the various Forerunner races in Andre Norton's science fiction novels.
 * In Jasper Fforde's Shades of Grey technology hasn't been lost so much as deliberatly purged by a series of "Leapbacks". Some is still reserved for the government resulting in Schizo-Tech.
 * The Liaden Universe has "OldTech", Clarkian technology from the waning days of the previous universe (as seen in Crystal Soldier and Crystal Dragon) and the early days of the present universe. Much of it was designed by or derived from tech designed by the Sheriekas, the evolved transhumans responsible for rendering that universe inhospitable to ordinary human life, and it can often carry their malign influence. One of the primary missions of the Scouts is to sequester or destroy any remnants of that technology that still exist, whether harmful or not, as well as research it to try to derive safe versions. This can sometimes bring them into conflict with others—such as Uncle or Clan Korval—who take a more enlightened stance toward using that technology. Likewise, the Department of the Interior recognizes the inherent advantage in having as much OldTech as they can.
 * The setting of Aestival Tide by Elizabeth Hand is a city run entirely on forgotten technology... which is slowly failing.
 * Elderglass from the Gentleman Bastard Sequence series.
 * The Deathly Hallows in Harry Potter. Each of them is a one-of-a-kind artifact with power that laughs in the face of all conventional magic: the Elder Wand when wielded by its rightful owner is powerful enough to repair other wands (which Ollivander believed was impossible) with a simple Repairing Charm, the Resurrection Stone can summon a bonafide shade from the afterlife (even this much shouldn't be possible), and the Invisibilty Cloak's power doesn't vanish with time (all other Cloaks eventually run out of juice). Attempts to recreate the Hallows have all ended in failure. Even the Elder Wand—wandmakers know that it's made out of elder wood and has a thestral hair core, but can't create another wand with its power even with those components available. The Hallows are so powerful and mysterious that one legend claims that Death itself created them.
 * Similar to the Shannara, example, The Empire of the East and the Books of Swords are set in the distant future of earth, after the collapse of technological civilization and the rise of magic. In Empire, however, Technology Comes Back, or starts to, at any rate. The discovery of some old technological devices, including an atomic-powered battle tank, plays a major role in the story.
 * Non-Stop by Brian Aldiss is set on a Generation Ship where the civilization has collapsed and lost technology is literally everywhere. For example, the plants that have turned the ship corridors into jungles are dependent on the artificial ceiling lights for photosynthesis.

Live Action TV

 * Pretty much the premise behind the Stargate Verse; on two distinct levels no less. Present day back to the era of the first Big Bad (Goa'uld), and their good counterparts (Tok'ra). And in later seasons from there to the even older Big Bad (Ori), and their good counterparts (Ancients). The "they were destroyed by their technology" part of this trope doesn't apply so much in this case, as the race which nearly all of the technology in question came from was wiped out by
 * In the Star Trek: Voyager episodes "Message In A Bottle" and "Hunters" the ship comes across a vast abandoned network of relay stations (over 100,000 years old; each powered by its own black hole!) enabling them to make contact with Starfleet on the other side of the galaxy.
 * The entire Andromeda series is centered around a big piece of Lost Technology.
 * Land of the Lost was full of this. In fact the Land itself was a pocket universe created by Altrusian technology.
 * Of the many worlds encountered in Spellbinder, both the Land of the Dragon Lord and the Land of the Spellbinders were based on lost and irreplaceable technology. In fact, Regent Correon's biggest goal in the series (besides helping Paul get home) is finding a way to repair power suits and flying ships- or construct new ones.
 * Dinotopia: The Advanced Ancient Acropolis of Poseidos has robot dinosaurs powered by Power Crystals.
 * Fringe has introduced this with an ancient race who developed the technology to destroy an alternate universe. You might not think that would be a useful thing, unless you just happened to be in the middle of a war with an alternate universe.
 * Not so contrived after all:
 * In Babylon 5, a great war resulted in
 * There's also companies like Interplanetary Expeditions, who travel to planets that were once home to long-dead civilizations, looking for Lost Technology among the rubble.
 * The source of the Rangers' powers in Chouriki Sentai Ohranger is technology created long ago on Pangaea that U.A.O.H. excavated.

Music

 * In Rush's "2112", the Tragic Hero finds an electric guitar, just to be told by The Omniscient Council of Vagueness that it's worthless and it caused the destruction of the elder race of man.

Tabletop Games

 * Lost technology and the remnants of a star-spanning Galactic Republic are a central part of the setting of Fading Suns, where mankind has descended into a new feudal age and most technology is considered sinful or even blasphemous by the Church.
 * First Age artifacts, especially warstriders, from Exalted. Subverted in that the technology isn't quite lost, just rare and only buildable in certain places or by certain people.
 * The Brothers' War that underpins nearly all of the early storyline of Magic: The Gathering was begun when the two brothers found the Lost Technology of the Thran.
 * The golden age of Humanity in Warhammer 40,000 was brought to an end around the 25th millennium by "soulless" rebelling robots known as Men of Iron and the advanced Standard Template Constructs that contained its technological knowledge were fragmented and scattered across the stars. The current Imperium of Man rebuilt human technology by recovering knowledge from these artifacts of the ironically-nicknamed "Dark Age of Technology". (The Dark Age of Technology is also, confusingly, known as the Golden Age of Technology. Whilst human technology verged on Crystal Spires and Togas at times, it is considered a spiritual dark age by the Imperium.)
 * There is also lots of other 'archeotech' out there from several of the other races, mostly the Slann/Necrontyr and the Old Ones/Eldar. It's heavily implied that three of the main races from the setting are forgotten and lost biological weapons.
 * Don't forget the Necrons, walking Lost Technology. They are ancient skeleton machines scattered through the universe.
 * The most spectacular pieces of Lost Technology are the Talismans of Vaul, aka Blackstone Fortresses. Giant, space-station-sized, quasi-sentient weapons capable of channeling pure Warp energy; and the only weapons capable of destroying the C'tan. Created by the pre-Fall Eldar, who, although they possess the necessary level of technology to reproduce them, no longer have the knowledge of their construction, or the resources necessary to rebuild them.
 * Also, of the six fortresses found,.
 * Gamma World is a haven for Lost Technology.
 * Basically anything more advanced than a lighter in Rifts is either lost technology or reverse-enigeered from lost tech. The Glitter Boy is a shining example of both - not only do most of the suits in existence come from before the Cataclysm, but the only new ones come from Free Quebec, who managed to work out their mechanics.
 * The exception being Magitek, the vast majority of which is imported from other worlds and/or dimensions; most notably the Splugorths via Atlantis.
 * Or home-built by Techno-Mages, who are VERY prominent in the setting.
 * BattleTech has 'LosTech' which is Exactly What It Says on the Tin. Well it's technically old Star League tech that was never proliferated, but don't go telling the Successor Houses that...
 * Most of it was lost, as the factories and personnel who made the lostech devices were destroyed and ComStar spent hundreds of years slitting the throats of anyone who rediscovered lostech items so they could hoard the lostech (which they alone retained specifications and production facilities for due to their neutral status) for themselves and take over the galaxy once the Successor States had sufficiently ruined themselves. Then the Gray Death Legion sold a Star League memory core with an entire database of lostech on the black market and put the kibosh on ComStar's grand scheme.
 * And then analysis of captured Clan tech led to advances that made even the coveted LosTech of a few decades ago look like toys.
 * The Fringepaths created by the Tehrmelern race in Fringeworthy.
 * Empire of the Petal Throne. Some examples of the previous human civilization's technology exist, but they're considered magical by the current medieval level society.
 * Third Edition D&D (and, by extension, Pathfinder) formally defined "lesser artifacts" as magical Lost Technology: items of great power that could no longer be manufactured by mortals. This distinguished such powerful, yet non-unique items (e.g. staff of power) from singular items like the Wand of Orcus. A few class features bend this definition by allowing the character to create a single specific artifact, but these come at or near the level cap where "mortal" becomes a questionable descriptor for the character.
 * Many published D&D settings have complex historical backstories involving long-forgotten civilizations, the better to account for why so much Lost Technology can be found lying around in monster-infested holes in the ground. This even applies to Eberron, the one setting with tech that is actively advancing, through the ruins of the extinct giant civilization, and Cannith ruins in Cyre (where it was lost within years of its discovery then found again within a decade).
 * In later editions of Cyberpunk, the 2020s DataKrash resulted in much technology being lost behind the Blackwall, still not to be recovered even by 2077.
 * In later editions of Cyberpunk, the 2020s DataKrash resulted in much technology being lost behind the Blackwall, still not to be recovered even by 2077.

Theater

 * The basic premise behind We Will Rock You, where music itself is the Lost Technology.

Video Games

 * A twist on this is Fallout, which takes place in a post-apocalyptic USA, beginning 84 years after a massive nuclear exchange that took place in the year 2077. The local Big Bad has recovered terrifying Lost Technology—in the form of a powerful nuclear weapon from the beforetime!
 * Well, it's post-apoc, so nearly everything in this game is Lost Technology. The best one? The G.E.C.K., of course. The Garden of Eden Creation Kit. That's saying Phlebotinum with four letters.
 * Although the G.E.C.K. has two different interpretations. Word of God once stated that the G.E.C.K. is far from being phlebotinum, but is more a farm-starter kit. Fallout 3, however, has it as an instant-terraforming device. Fans have a number of ideas for the discrepancy, the most obvious one being that, of course, it's a new developer and They Just Didn't Care.
 * Central to the Halo series; the entire setting is one giant piece of Lost Technology.
 * Though, it's also a subversion. It's not useful besides for taking over for living on (unless you're an idiot and let out the Flood), and if you do use it you DIE. Also, all the OTHER tech sucks or tries to kill you... or both.
 * Off-screen, Forerunner technology was what fueled the creation and technological advantage of the Covenant. The Prophets had the Forerunner Dreadnought and, after taking to the stars, kept looking for more. The entire war against the Hunter was because some of them ate the stuff.
 * JRPGs are fond of this, especially Square:
 * Nearly every early Final Fantasy game has some elements (6 and 7 as Lost Magic), usually just to give you a chance to dungeon crawl through a high-tech tower of some sort. No one ever thinks to pick up a dropped laser gun or study the tech for the betterment of the world, though.
 * Well they're quite happy to put it all to good use in Final Fantasy X. The Al Bhed ignore the anti-technology taboo that everyone else has, and have built their entire society around salvaging ancient "machina" for reuse.
 * A major element in Wild ARMs 1 and Wild ARMs 3. In fact,
 * Xenogears tends to flip-flop on whether Gears are or aren't lost technology. At the very least, Gears are dug up from ancient ruins, but it's painfully obvious that they can be tweaked and created via available tech in the more advanced areas. At the very least, the Omnigears are lost tech.
 * The remains of the Elridge, however, and the Zeboim civilization, very much fit the trope. The Merkaba, the "Treasure of Kislev," the Yggdrasils, and Emeralda herself are primary examples.
 * Carried through to its spiritual prequel Xenosaga, archeologists digging up the Zohar and building the Zohar Emulators, a technological bridge to higher planes of existence that is responsible for the historical divine miracles and a theoretically infinite source of energy. In true lost tech style these higher planes also contain the Wave Form Existence/God/Chaos/U-DO, the big bad of the series.
 * Secret of Mana centers around the attempts of the Big Bad to acquire the ancient world-destroying Mana Fortress and Mana Beast.
 * In Brain Lord, you fight through many gimmicky Lost Technology dungeons.
 * Chrono Trigger has different technology available in different eras. As the game is based on Time Travel, however, if something is Lost Technology in the modern era, you can go to the era where it was developed and where it's not "lost."
 * The Enlightened Ones of Zeal in 12,000 BC use Magitek that no era, not even the future, can match. However, when Man Grew Proud and Zeal fell from the skies, the knowledge of Zeal was Lost Forever. Though relics from the Dark Ages survive, such as the Masamune, the Sun Stone and the Pendant of the Guardia royal family, the power of magic was lost to humans, Magitek was never rediscovered, and technology in the future went down a purely nonmagical path.
 * In one specific case, the red mineral called Dreamstone was commonly used to make powerful technological and magical devices during the Dark Ages, but all sources of it have dried up by the modern era. This becomes a problem because, while Melchior has the technological and magical knowledge to reforge the Masamune, he doesn't have any Dreamstone to use in the alloy, necessitating a Fetch Quest in 65,000,000 BC.
 * Prior to The End of the World as We Know It in 1999, human technology had advanced to levels roughly equal to the Enlightened Ones, but all of that ended on the Day of Lavos. In 2300, humans are no longer developing new technology, and humanity only clings to existence by maintaining 300-year-old relic machinery.
 * 65,000,000 BC is an odd situation. The Neanderthals are Stone Age hunter-gatherers, but their craftsmanship is good enough to develop weapons superior to anything available in the modern world, including guns and robotic arms. Though this is partly Gameplay and Story Segregation (especially the Stone Arm), at least part of it is implied to be through the use of Dreamstone, which the Ioka Tribe knows about but, as humanity has not yet evolved magical abilities, cannot utilize to its full potential. No weapons from 65,000,000 BC are known to have survived in any other era, but you can take them to the future yourself if you choose. Also, Elixir is freely available to the Ioka (and called Sweet Water), but after the coming of Lavos, the Sweet Water stops flowing and Elixir becomes a fairly rare item afterwards.
 * In Mass Effect, a large part of the story revolves around the galaxy's dependence on Applied Phlebotinum that were created by the Protheans, a mysterious race that died out 50,000 years ago. However,
 * In Mass Effect, a large part of the story revolves around the galaxy's dependence on Applied Phlebotinum that were created by the Protheans, a mysterious race that died out 50,000 years ago. However,


 * BioWare also invoked this Trope with Knights of the Old Republic. The Rataka technology and Star Maps were an unholy cross of well-built, heavily-guarded technology infused with the Dark Side of The Force. A virulent plague, slave revolts, warring amongst themselves, and a mutation rendering the species Force-deaf sent the planet back to the stone age. By the era of Darth Bane, the species is extinct, meaning any hope of recovering the tech is lost forever.
 * Metroid's Chozo had marvelous technology, widespread over many a planet the player visits in a game, all of which Samus inevitably collects, blows up or uses during the plot to refill her Bag of Spilling.
 * Ditto for their oneshot intergalactic Pen-Pals, the Luminoth.
 * The Xbox remake of Ninja Gaiden features a statue with floating stones. This power, it is said, "clearly shows that it was not made with modern technology" and "must be the product of an ancient age". It becomes important later.
 * The RPG Dokapon Kingdom actually has an item CALLED "Lost Technology." It unlocks a new character class, the Robo-Knight—male characters who use it become Sentai-style mechs, while female characters become Robot Girls.
 * Mega Man Legends is all over this trope. From the setting to the plot to the Big Reveal at the end of the sequel to the world's money, it all has to do with Lost Technology.
 * Might & Magic.
 * The cultivators in Thief 2: The Metal Age.
 * Av Kamiw in Utawarerumono. Basically, giant Evangelionesque mechas in a world where a very few persons like herbalists know of gunpowder, and fear it too much to use it. Game Breaker much? (They still go down to swords and arrows then it's the protagonists attacking, of course.) The last stage of the game is also set in an abandoned research laboratory that has a few crumbling remnants of working technology, but it's generally useless stuff like holograms that tell us about the backstory.
 * Neverwinter Nights gives us the incredible magic of the Old Ones (lizard-people precursors) (who used it to create a stasis shelter to protect them from global cooling) and the powers used by the people of Netheril to levitate their cities.
 * In the Netheril case, it ultimately came from the mother setting, with an interesting explanation for why the ability to shear the tops of mountains and levitate them were lost: the old method to do so became impossible to use when the rules of magic were re-written.
 * Neverwinter Nights 2 gives us the Illefarn Big Bad, created with Lost Technology, and their Song Portals (which can be duplicated at greater expense by modern magic.)
 * The Jak and Daxter games feature the shiny orange artifacts, structures, and machinery of the Precursors.
 * Played with in Tales of Symphonia and Tales of Phantasia, where magitechnology was lost, but is just being rediscovered. In both cases, as well as during the 4000 years inbetween, one of the first pieces of technology to be reconstructed and rebuilt by archaeologist/scientists is the Mana Canon, the superweapon the use of which destroyed the ancient civilizations that invented (and reinvented, and re-reinvented) magitechnology in the first place.
 * Done by a Mad Scientist bad guy in favour of genocide and the opression of human beings planning to usurp power within his organisation.
 * Played with further in Tales of Vesperia, which revolves around "Blastia": Lost Technology that is well-researched, widely-used and vital to modern life in the world. Even though the knowledge on how to create blastia has been lost, research has advanced to the point where basic preliminary models can be created. In another subversion of the usual formula, the solution to the heroes' problems is not using them.
 * The earlier Shining Force games features a cast of traditional fantasy warriors, magicians, and creatures battling traditional fantasy evils. Except for the occasional sentient robot that survived through time to help the heroes.
 * In Phantasy Star IV, society has reverted to simpler, medievalish technology after . Unfortunately, without her guidance, the technology controlling the planetary systems like climate, tectonics, and defenses, goes haywire and makes life tough for the survivors. At least until the heroes beat the Big Bad and
 * Interestingly, for being lost technology, a lot of it  Instead of exploring the obvious choices, archeologists were convinced random caverns held better secrets.
 * It's implied that the system installations that are out in plain sight are either impossible to get to due to environmental hazards (the ocean, a high population density of dangerous sand-worms, a cult) or protected from entry with dangerous laser barriers that were designed to keep humans out. Birth Valley is a huge discovery because there isn't anything stopping anyone from getting in (other than scary rumors).
 * Dwemer technology in The Elder Scrolls series. Because the Dwemer studied the laws of nature as they were being created, they were able to manipulate said laws to empower and protect their creations in a way no other race can achieve.
 * The main premise of the Uldaman and Ulduar dungeons in World of Warcraft - though unsuccessful in both cases.
 * Gnomeregan is realtive case. The Gnomes of WoW are the most technologicaly advanced people on Azeroth (all the way up to friging Nuclear Bombs) but they lost their city to a Trogg invasion during the 3rd war (some 7 years ago at the moment) and with it the best of their tech. Its a lowbie dungeon now and one of the most run for all the enginering drops. They rely on Steampunk style tech mostly now (but they still have shrink rays and rocket launchers) but spend their time trying to (fuitlessly) retake there home.
 * They're achieved partial success in Cataclysm. They now (somewhat) hold the upper part of the city.
 * Assassins's Creed II has
 * The fifth game in the Thunder Force series is about the discovery of a wrecked ship that humanity calls "Vasteel" ("Vastian's Steel" for short) and builds a line of technology based off it, including a supercomputer...which goes berserk.
 * Discussed in a tavern conversation in Infinite Space. A character notes that Adis' advanced technology is very close to the technology their precursors from Earth Terra used to have, which leads another character to say the idea of their precursors had more advanced technology than the current generation is ridiculous.
 * Various artifacts from the Sindar civilization in Suikoden series.
 * The artifacts of the Xel'Naga in the StarCraft series. Even Protoss technology pales in comparison.
 * Retrieving their Lost Technology is one of the major reasons the Dwarves continue to launch expeditions into the Darkspawn infested Deep Roads in Dragon Age Origins. Some of the lost thaigs still hold valuable secrets that could help turn the tide against the Darkspawn. Others have secrets that are better off buried and forgotten.
 * Very common in The Legend of Zelda, where a few centuries prior to The Legend of Zelda: Skyward Sword, there was a thriving civilization made up mostly of sapient robots (and, probably, a related civilization that made the robots), with antigravity technology, mastery of electricity, and other technology to put modern Earth to shame. The civilization vanished around the time of a war against the Bigger Bad, and ancient ridiculously high-tech relics show up in dungeons and as monsters for the rest of the series, a span covering literally thousands of years.
 * Sword of the Stars is rife with Precursor-tech, unfortunately most of it is shooting at you in the form of random encounters. The Morrigi in particular were once much more advanced than they are now and most of their "research" is simply re-discovering what they're lost.
 * One form of treasure in the post-apocalyptic Roguelike Caves of Qud.
 * In the backstory of Dark Souls the Witch of Izalith and her Daughters of Chaos were originally wielders of flame sorcery. The Witch's disastrous attempt to recreate the First Flame with her Lord Soul of Chaos mutated her and most of her Daughters (only Quelana escaped unscathed). The original flame sorcery was lost and replaced by Pyromancy. The only traces of the original sorcery are the Demon Catalyst wielded by the Demon Firesage (the last practitioner of the flame sorcery whom you eventually kill) and the Izalith Catalyst that belonged to one of the Daughters of Chaos prior to the birth of Pyromancy.

Web Comics
"Lt. Harley Sorlie: People have been suckering each other with "secret of the ancients" scams for thousands of years. Claiming that some lost technology has been re-discovered is pretty much the same as saying "I am running a con" Ennesby: So you see our problem [...] We want to sell actual re-discovered technology, but our potential customers all think they're too smart to buy it."
 * The dragons' Iridium Bomb in the second story arc of The Inexplicable Adventures of Bob.
 * Wapsi Square has the golem girls as well as the calender machine. The former were responsible for destroying the civilization that created them, while the latter
 * Schlock Mercenary played with this when Oafan delegation rode in on a huge ship. As mentioned on the previous page, it uses a rather crude and hideously dangerous gun, and some of more advanced stuff turns out to be necessary simply to survive side effects of their own weapon system. Also...

Web Original

 * In Fine Structure, one of the protagonists
 * Land Games:
 * SCP Foundation; SCP-001 (ROUNDERHOUSE's Gold proposal) is a city founded by the Mekhanites, the ancestors of humans who would found the Church of the Broken God, and is full of this. The city had mass transport, flying machines, motorized war machines (including Humongous Mechas) and cold fusion generators at a time where most humans were only in the Bronze Age, though most of it was broken in a terrible war against Daevites, the Sarkites and later the Abominate. Even modern Mekhanites can barely comprehend how they work.

Western Animation

 * In the Futurama episode Mother's Day, Fry reinvents the wheel (which he shapes like an oval) after the robots rebel.
 * In a later episode, the crew go to a museum to find and use a thousand year old weapon... The heat-seeker missile.
 * It's also been suggested that, at some point during the time that Fry was cryogenically frozen (possibly during the 24th Century), the world had experienced another Dark Ages. Yet, somehow, Fry remains cryogenically frozen during that time.
 * Many of the Arkadian devices in Spartakus and the Sun Beneath the Sea could count as Lost Technology; their creators died long ago and nobody today knows how to fix them - which is Very Bad because their artificial sun is dying.
 * Xyber 9, the Garden of the Ancients, battle medallions/battle armor, and probably most of the tech in the Underworld of Xyber 9: New Dawn.
 * In ThunderCats (2011) the Cats of the magical kingdom of Thundera, stuck in Medieval Stasis, consider technology to be the stuff of fairy tales they tell their cubs, and any physical evidence thereof as Worthless Yellow Rocks forged to take in the gullible. Young Prince Lion-O believes otherwise, and scours the Black Market for salvaged tech. Unfortunately, technology is very real, as their longtime rivals the Lizards prove when they ally with a benefactor to unleash a Superweapon Surprise, using shockingly futuristic war-tech like Humongous Mecha and laser rifles to conquer the Kingdom of Thundera in one night.

Real Life

 * A great many of the Romans' construction techniques, such as how to make aqueducts, were lost for centuries once the Roman Empire collapsed, and the remains are still around today.
 * The Romans had used concrete to create buildings with domes. Once the Western Roman Empire fell, no large-domed buildings were able to be built until Brunelleschi's Cathedral of Florence was completed in the Renaissance. There were domes in the Middle East before the Renaissance, however, as they were inspired by the Hagia Sophia and other Byzantine churches.
 * One of the reasons the secret of concrete was lost was because the Romans used a specific type of Italian volcanic ash as a binding agent. Attempts to duplicate the concrete recipe without access to that ash would fail, until a substitute was developed in the 1600s. Even modern concrete isn't quite as durable as the Roman type; some Roman buildings are still standing after 13 centuries or more.
 * Also, depth in paintings... if you look at some of the murals from Pompeii, they might well have been painted in the 1600s for how realistic they look.
 * This is probably the ultimate origin of the prevalence of lost technology/lost glory tropes. Consider that Greco-Roman cultures achieved a level of civilization and technology that is still admired today, to say nothing of aesthetic refinement - and within a surprisingly short time, it was all lost. Today we take for granted that things will improve with time, or at least not get worse, but Europe went from working sewers, running water, magnificent architecture, rich art and literature, and extensive trade networks to filthy wells, septic holes, ramshackle dwellings (even palaces in the dark ages were pretty nasty by modern standards, whereas Roman buildings would be considered primitive but habitable), virtually no literacy outside the clergy and little art or literature that isn't church controlled and rather primitive compared to what came before - to say nothing of the complete lack of extensive trade. And they were surrounded with ruins of a far superior civilization. Yeah, that probably made an impact on our collective conscious.
 * Though even then they were, in many cases, looking at the wrong things at times. The overall technological level of Europe actually increased after the fall of the Greco-Roman civilization, and many important inventions were made or came to the continent only after that civilization fell - stirrups, for instance, were introduced over a century after the fall of Rome, and in any case, not all of the Roman empire fell at once, with the eastern portion of the empire surviving another 600 years. Some things were lost, though, such as the ability to make highly advanced gearing.
 * Another possible origin is simply that the balkanization cut down traffic and thus decreased the resources available that could be spent on large technological projects like roads and aqueducts.
 * Even as The Dung Ages unfolded after the fall of the Greco-Roman cultures, people's ingenuity still worked, if their living depended on it. Something like this, but stronger and made of metal, you may find in your nearby hydropower plant, or in your car's turbocharger. But these turbines have been known at least since the Late Middle Ages in water mills. The best part of it? The craftsmen who built them were in most cases illiterate and most certainly had never known maths.
 * So-called "Damascus" steel has been lost for centuries since the original iron deposits in India ran out (there was a key impurity in those particular iron deposits).
 * It was figured out in the late 1990's and there are now companies making bladestock from it. Modern bladesmiths have slowly been using it more and more. To prevent confusion with "Pattern-welded" steel, which was and is commonly referred to as "Damascus" steel, it is known by the original name for the ore: "Wootz".
 * Damascus steel was dependent on both the Wootz ores, and a complex heat-treating and tempering process that utilized the unique characteristics of the trace impurities in the wootz ores. It was the recent rediscovery of both the type of ore and the heat-treating process that allowed the replication of Damascus steel.
 * This is also a case of parallel evolution. Japan possessed iron ores similar to the Wootz ores (though inferior in production and more difficult to mine and refine); and developed an even more advanced tempering and construction technique to take advantage of the nature of the steel, and compensate for its scarcity. Unlike the original Damascus steel, the techniques were well-documented and passed along, instead of being kept as closely-guarded trade secrets.
 * There is also Greek Fire, which could not be put out using water, of which the formula has been lost for ages.
 * Today the problem of finding out what it was is more related to the fact that there are several options. There is more than one known way to make fire that can't be put out with water, as well as conflicting accounts of how Greek Fire actually behaved; some say it ignited on contact with water, others say it only needed to be exposed to air. Quite possibly it's a catch-all term for a number of different incendiary chemicals, some or all of which may have since been rediscovered.
 * The US goverment forgot how to make a material used in trident missile production codenamed Fogbank.
 * Technology Marches On: According to that other wiki Fogbank was successfully reproduced in 2007 and the first refurbished warheads containing it will be transferred from the DOE to USN in fall 2009.
 * As far as LosTech goes, FOGBANK is a special case on a par with the legends of the katana; apparently the first new batches, made according to the documented methods, were non-functional, due to a lack of certain impurities which went undetected during the initial production in the 80's. This has been dealt with and they are now manufacturing new FOGBANK.
 * The Antikythera mechanism was a mechanical device for computing the position of the Sun, Moon, and the planets from a date and time. Its parts are on par with 18th century clocks in terms of complexity. It was made in the 2nd century BC.
 * The Stradivari violins were made using secrets that were given from master to apprentice, and most of those secrets are lost today.
 * Plenty of studies have been made with high-tech equipment on these violins to find out the hidden factor. At the moment, the primary component is suspected to be the quality of the wood, which is ever so slightly rotten to give it its unique sound. Experiments are being made to replicate the technique, but since the Stradivarius-violins are so old and expensive, the chances are that it will take longer to convince people that new violins can sound as good, than it will take to actually make them.
 * The most recent studies have more or less concluded that the characteristics of the Stradivari violins were due primarily to three factors. 1) The use of salt-water cured wood (logs were stored for long periods in the commercial harbours before being dried and sold. This broke down the lignins in the cell walls, resulting in a more flexible, more resonant wood. 2) An unusual varnish incorporating ground quartz; a mineral with unique electro-mechanical properties. The quartz particles acted as a sort of resonance filter, damping high-frequency harmonics and resulting in a mellower tone. 3) Some quirks in the manufacturing and tuning process unique to Stradivarius and his students.
 * The fact they were made from wood that grew to maturity during the "little ice age", when cooler temperatures caused narrowing of tree rings, may also have been a factor in their quality.
 * The wood is now more than 300 years old. Also, music has been continuously been played on those instruments for 300 years or so. How this affects the resonant properties of wood is not fully understood, but brand new violins tend to open up and improve over time until the wood decays to the point of deterioration, provided there are no structural failures and the instruments are maintained properly.
 * Said studies however, are only on the properties of the wood. The famous "Italian sound" of the violins on the other hand, is a completely different story altogether. It is worth noting that Stradivari violins do not perform particularly well in blind tests, which have repeatedly failed to find any significant differences between them and the best modern instruments (an example of which can be read here). It is very common for the more modern violin in any such test to be identified as the "Stradivari," which is taken to mean the best violin of the ones being tested. This even occurred in a blind test when two violin experts were allowed to play the instruments, and still could not correctly identify the Stradivari. In double blind tests, where neither the players nor those carrying out the test knew which violin was which, even experienced violin makers failed to identify the Strad or Guarneri and often end up preferring a modern instrument instead.
 * Speaking of blind tests, audiences and expert violinists and even experienced makers alike have been completely fooled when a modern violin was deliberately introduced as a Strad or Guarneri and the real violins as ordinary instruments, which suggests that psychology has a major impact on the way human beings hear an instrument. Over and above that, while there is agreement on what is a bad sound, but what constitutes a good tone itself is too subjective to draw any conclusive ground.
 * Other than some unique properties of the wood, everything else may actually be an aversion of this trope. Every Stradivarius and Guarnerius violin being used today has been extensively modified over the last 300+ years since they were built. The fingerboard has been thickened and lengthened, the nut redesigned, the wood strip connecting the fingerboard to the neck removed and replaced by an all ebony board, the angle of the neck reset (in some cases, the neck itself was replaced) for higher inclination of the strings and the design of the bridge completely changed to the point where it doesn't resemble anything close to how a bridge looked in Stradivarius's time. The sound post, bass bar and tailpiece have all been changed as well. Then the chin rest and shoulder rest were also thrown in. Any professional violinist would know that changing even one of them would have a major impact on the sound, response and ease of playing. And that's not all.
 * The strings have also gone through considerable improvements since Stradivari's time, all for the sake of improving the sound and response of the instrument. First wound gut strings were developed and then steel, then synthetics and alloy strings came along. Today there are dozens of brands offering different types of strings in different gauges and it is all modern technology. The strings are the single biggest variable in the sound production of any violin.
 * Everything mentioned above constitutes the setup of a violin. A setup that works well for one person's physique may be very uncomfortable for another person. Comfort and ease of playing is no small factor to be taken lightly.
 * Not to mention improvements to the bow. Modern violin technique would not exist without it. The development of the modern bow since the time of Francois Tourte had a remarkable effect on the timbre of violins, allowing for much more power and meeting the demand for expression and technique required by the music that was being composed at the time. The bow is half of violin playing and great violinists could be very particular about the bows they wanted. Over and above the improvements in sound, the mechanical properties of a very good bow facilitate an enormous range of tonal expression and technique which would be impossible to achieve on an inferior bow. Music from the time of Beethoven onward just cannot be played with the kind of bow that existed in the late 17th and early 18th century.
 * The technological developments go way beyond the violin itself. In sound perception, the acoustics of the concert hall matters more than one can imagine. There is a huge difference between the sound heard under the player's ear and the sound as heard by the audience due to reverberation, etc. The violin is not actually a loud instrument. A beautiful sound up close heard within the confines of one's practice room may be totally inaudible on stage against all the other instruments playing. Some violins (both old and new) that do not sound very loud under the ear on the other hand, project very well into a hall at a distance. A very good violin has the ability to selectively "beam" different frequencies in different directions. The acoustics of concert halls plays a very important part in projecting the best tones and frequencies, and the best concert halls in the world from the late 19th century onward are renowned for this. The acoustics can mask noises and even mild intonation errors.
 * A soloist in an ensemble playing on a powerful violin that is placed too close to the mike can sound scratchy, harsh and anything but musical, but when heard in a concert hall from farther away the harsh tones are damped out by the auditorium itself and the tone at the audience end has been described to be incredible, rich and colorful.
 * And recordings. The way a violin sounds in a studio recording (especially the older ones where the soloists where miked much closer) can be very different from how it really sounds in a concert hall. This can give the listener a misleading perception of the sound of the violins used by the soloist. A graphic equalizer can modify the instrument's timbre to the point where it sounds nothing like the original. The quality of the audio equipment can make a significant difference too.
 * The single biggest variable in the violin sound is the player. There are numerous occasions where expert violinists have taken the inferior instruments of their students and reproduced the same incredible sound of their own violins. It is also well known that different players sound totally different on the same instrument. There are extensive documented cases of great violinists being unable to reproduce their tone when having to play on an unfamiliar instrument.
 * In fact, the Stadivarius and Guarnerius lore might be a major case of YMMV. There are many experts who hold that there is no such thing as the Stradivarius secret and the mystique around it is just a romanticized brand mythology for the market to keep raising their prices higher and higher. Old instruments are a valuable investment and some sell for millions of dollars.
 * A tool similar in exquisite manufacture, reputation, mystique and expense to a classical-age violin is the classic double rifle from the golden age of African hunting. Contrary to what people may think, their number during The Edwardian Era was never large (the vast majority of hunters and workers in the African colonies could not afford something more expensive than a demilitarized rough and tumble bolt-action rifle) and insane expenses are needed to achieve in modern times the same performance it did 100 years ago. One may find out the hard way the $120,000 classic rifle once fired by Denys Finch Hatton needs a caliber which no factory has built since the 1950s, is regulated to a precise combination of powder (which is no longer manufactured) and bullet weight and aerodynamics that no archive search can find, and finally the modern target shooter lacks the Great White Hunter's talent, or is so different in body shape the rifle doesn't fit him or her the slightest bit.
 * The so-called Baghdad Batteries (which are technically fuel cells, not batteries). While significantly less powerful than that 99 cent Duracell you buy at 7-11, and requiring an entire vase (not a cheap item in those days), they were fully functional 1800 years ago. Naturally, this raised the question of why people made them in the first place. While no one actually knows for sure what their intended purpose was; archaeological evidence indicates that they were most likely used for electroplating gold (which would not require a large current).
 * The schematics for the Apollo vehicles, which were written on computers that no longer function, and cannot be read with modern computers. See No Backwards Compatibility in the Future.
 * It is at least possible to rebuild the control computer from Apollo 11
 * The computer controls are the most out-dated part of the whole thing.
 * The A-10 Thunderbolt, only 715 of which were made, and in part has No Plans, No Prototype, No Backup (see here; the plans existed, but many of them were thrown away after the subcontractors went out of business), so spare parts have to be scavenged from non-functioning planes.
 * Although thanks to its durability and primary ability, not too many of them are needed.
 * Couldn't they just pull a few apart to figure out how to manufacture the parts again?
 * Apparently it's easier to just create compatible new parts without regard for whether they're different from the originals.
 * The Telharmonium, the first electronic music instrument.
 * Not really lost. The relevant patent documents are available (US patent #580035, dated April 1897, and related patents filed by the inventor), and it would be trivial to rebuild the machine. Of course, a modern Yamaha synthesizer can do everything the Telharmonium did and more, without the inconvenience of weighing almost 200 tons...
 * Nowadays there is an entire branch of archaeology dedicated to fabricate and use replics of ancient tools just to determine what the heck were they used for. It has helped greatly to understand prehistoric lithic industries, though there are still items of unclear function, such as the palaeolithic "sceptres" found in many places.
 * Most of the legendary Atlantean and Vedic technology, such as fire crystals and Vimana. Of course Your Mileage May Vary on whether this is genuinely Real Life or not.
 * Techniques of forging relics, especially that of Turin Shroud. We know for certainty that it is a Medieval forgery, but we have absolutely no idea on how it was forged.
 * Heron Alexandrinus (10-70 AD) made (supposedly first): steam turbine—ages before the piston steam engine that first got on trains and boats; several self-regulating feedback control systems—precursors of things like the regulator which made possible the steam engine (and again) as we know it; and a slot-machine—drop a coin, get a drink.
 * Heron also described earlier (attributed to Archimedes) inventions, including an odometer, both in taximeter and naval log variants.
 * According to Aristocles (2nd centrury BC), there was an alarm clock in Plato Academy.
 * Around 424 BC Boetians burned down wooden walls of Delium. With a bellows-powered flamethrower.
 * Aside of an organ (hydraulis), which was the first keyboard musical instrument ever—and, by the way, quickly found its place as a church organ —Ctesibius invented: a pump (ironically, it was lost in the fires that ravaged Alexandria); a water clock (a direct precursor to the flushing toilet); solar-powered mechanisms and a pneumatic cannon. In the third century B.C.
 * Archimedes, according to Leonardo da Vinci, also built a steam-powered cannon.
 * The Chinese magazine-fed crossbows (Chu-Ko-Nus) are rather famous, but there were more advanced forms. The first known chain-driven weapon was not "Chaingun", it was the chute-fed Repeating Catapult by Dionysius of Alexandria.
 * This means it wouldn't have required anything new to have full-auto turrets centuries before anything similar appeared. Add steam artillery and pumps above for complete Schizo-Tech imagery in the vein of quadreme battleships -- Wooden Ships and Bronze Men, if you want.
 * Fully mobile artillery was known at least in the Roman era. The Ballista quadrirotis was simply a two-horse cart with a ballista on top, but it was enough to make a field artillery with a significant level of maneuverability.
 * Götz von Berlichingen, the knight most renowned for his wit due to Goethe, designed a mechanical prosthetic iron hand for himself to replace his right hand and forearm lost in combat. It was so advanced anatomically that it could handle the reins of a horse, the shaft of a lance, a playing card and even a feather quill to write a letter, while modern age prosthetics designers studied it as a model. But there was one thing the 16th century lacked—the energy source (springs would be either too weak or too big) -- the hand needed first to be tightened by the other hand around the object to be handled.
 * The field transistor predates the bipolar transistor by 22 years (Lilienfeld filled the first patent application in 1925), since the idea was much closer to the electron tube. It's unlikely that he really built it: considering the proposed scale and the quality of early semiconductors, it would not give a measurable amplification. But the principle was right, even though the theoretical basis was not yet developed.
 * Another Chinese example would be the south-pointing chariot
 * We have had modern lasers for over half a century. For much of that time the technology was described as "an elegant solution lacking a problem".
 * Someone might have figured them out much earlier. There was a 18th century scientist called Sir Henry Cavendish who was ahead of his time in a few areas but was unfortunately regarded as a bit of a crackpot and therefore largely ignored. In 1921, someone finally got around to examining his surviving lab equipment and experiments and, among other things found a glass tube full of argon with mirrored electrodes inside which suggests that he was at least on the brink of creating an argon laser.