Secret Path

""We will take you on safe paths, through the mist. Come Hobbits come! We move quickly. I found it, I did. A way through the marshes. Orcs don't use it. Orcs don't know it. They go round for miles and miles.""

- Gollum, The Lord of the Rings: The Two Towers

""I know a secret path through these mountains.""

- The 300 Spartans (1962 film)

Suppose there's somewhere you need to go, but getting there could be difficult or dangerous. Maybe you have to get into a walled city, castle, or Supervillain Lair, but the entrance is guarded by armed soldiers or a Golem. Maybe you have to cross a minefield or an uncharted deadly swamp where one wrong step could drop you into a pit from which you would never return. Maybe you've gotten into the enemy base and need to go to the control room, but you suspect that the main hallway with signs saying "control room this way" has more security cameras than all the other hallways combined. Maybe there's a range of mountains you need to cross, but your map doesn't show any pass nearby. Maybe you just need to go from one town to another, but you're a widely recognizable fugitive and don't want to be seen by other travelers on the road between them. Whatever the reason, there's somewhere you have to go, and obvious ways to get there either don't exist, would take too long, or would be near-suicide to use. If only there were some special route that's not widely known, one that could get you where you need to go while bypassing many of the obstacles in the way...

What you need is a Secret Path. This is a passageway that not everyone knows about that can be used to get somewhere that is difficult to reach or to go somewhere without being noticed. Sometimes a local guide will be knowledgeable about paths that outsiders are unfamiliar with.

Although these Secret Passages are sometimes lauded as "shortcuts," they can sometimes take longer than more obvious paths, and can be laden with treacherous hazards that make them even more dangerous than the danger they allow travelers to avoid. Expect any secret path through a swamp to be unpleasant, since Swamps Are Evil.

Common types of secret paths include back doors, Bookcase Passages, ventilation shafts, and underground routes such as passages through Absurdly Spacious Sewers. See also Right Under Their Noses, Hidden in Plain Sight. If you make your own secret path, it's called Dungeon Bypass. A Secret Path can turn a Great Wall into an Absurdly Ineffective Barricade.

Anime and Manga

 * Princess Principal has two, one only existing in flashback (the way into the castle that Ange discovered and explored, resulting in her meeting Charlotte for the first time), and the other in use during the series (the secret tunnel between Queen's Mayfaire school and the garage where Ange and Charlotte keep their cars).

Film

 * Clue had one.
 * Involved in one of the It Was Here, I Swear gags in Abbott and Costello Meet Frankenstein.

Literature

 * Prydain Chronicles book The High King. Achren leads the heroes along a hidden path over Mount Dragon into Annuvin, avoiding the dangers of other routes.
 * In The Lord of the Rings:
 * Gollum leads Sam and Frodo through the Dead Marshes, using a path that the orcs don't know.
 * Lord of the Rings also has the path the Rohirrim take to get to Minas Tirith, led by Ghân-buri-Ghân.
 * The hidden West-Gate into Moria, effectively a secret passage to everyone but the Dwarves ... and their friend.
 * Meanwhile, back in the Shire, young hobbits would occasionally search for hidden passages in Bag End, convinced that Bilbo had concealed his legendary wealth there.
 * The Hobbit has a Dwarven door in the Lonely Mountain that foreshadows the later book's Moria gate—a secret passage into the very heart of the Lonely Mountain whose keyhole only appears on the rarely-occurring Durin's Day and whose key was lost for years.
 * In Harry Potter, Much of Hogwarts castle is built with several secret passages that the students use to get around school quickly. The castle has so much and some are so well hidden few people know the exxact locations of each one. The only three plot significant secret passages used in the books are passages leading into Hogsmead Village:
 * One leading to the cellar of Honeydukes candy store.
 * The Castle Canyons are secret passages in the Castle of Septimus Heap. They are used by Jenna, Septimus and Marcellus Pye in Darke to get around while the Castle is swamped by a Darke Domaine.
 * The Castle Canyons are secret passages in the Castle of Septimus Heap. They are used by Jenna, Septimus and Marcellus Pye in Darke to get around while the Castle is swamped by a Darke Domaine.
 * The Castle Canyons are secret passages in the Castle of Septimus Heap. They are used by Jenna, Septimus and Marcellus Pye in Darke to get around while the Castle is swamped by a Darke Domaine.

Tabletop Games

 * In Dungeons & Dragons secret passages are fairly common. So common that ability to detect secret doors is listed as an elven trait rather than in section(s) about the secret doors themselves (and for that matter, dwarves can notice unusual stonework).

Video Games

 * Roguelike Omega included secret mountain passes, which cut down on travel time in the wilderness.
 * In Skies of Arcadia, there is a passage through Valua's sewer system that leads to the arena in the Coliseum. The sewer system can also be used to travel from Lower City to Upper City, even though free travel from Lower City to Upper City is supposed to be forbidden.

Web Comics

 * In The Beast Legion Master Surya reveals an underground passage to the anointment room in Issue 5.
 * Girl Genius has this invoked - Lars searches for a secret passage, like "in all the stories". But since all those evil geniuses are also inclined toward theatrics, there actually is one.
 * Crimson Dark has a whole "labyrinth" of secret corridors through a (part-military) orbital port. Which allows to avoid the customs. Of course, even if outsiders catch he wind of it, anyone met there is going to be high-clearance military or security personnel or be escorted by these...

Web Original

 * RWBY: At the end of Volume 4, Weiss escapes the "house arrest" in the Schnee mansion imposed on her by her father through a secret passageway behind a bookshelf in the house's library, revealed to her by family butler Klein.

Western Animation

 * Sewers are good for this; that's how the Gaang gets back into Omashu in Avatar: The Last Airbender. There's also supposedly a "secret river" (but not secret enough not to be discussed in Fire Nation grade school) that leads to the Fire Lord's palace.

Real Life

 * According to historians like Herodotus, Xerxes gained an advantage in the Battle of Thermopylae when a Greek named Ephialtes told him of a mountain pass around Thermopylae, at which point Xerxes secretly sent 20,000 Immortals under the command of Hydarnes through so that the Persians could have the Greeks surrounded.
 * When naval minefields became a common tactic in modern war, the defenders would have pilots (small-craft captains) who could guide friendly shipping through a safe path. Assuming that none of the mines had come loose and drifted into the path you were using.
 * Externally powered minefields were solid, however: on low alert, the mines' circuits were simply turned off and won't react on a ship, and on high alert galvanic stations could deactivate a section, let friendly ships pass and then flip the switch back to close the passage.