Trope Workshop:Land of Shattered Empire

A common element of an Adventure-Friendly World is that the setting is set upon the ruins of a now defunct empire. This allows creating a world without a central authority to solve problems, and several factions willing to wage war (either open or espionage) on one another, while maintaining several conveniences one would spawn such as a common language, and a shared history, as well as allowing for now international institutions, standards and/or road networks (which are often in disrepair and plagued by bandits, often ones dumb enough to attack heavily armed and armored men). One or more of the factions may claim continuity with the old empire.

See also Balkanize Me, which may well happen to such an empire if it spanned a large enough collection of peoples and cultures.

Tabletop Games

 * Eberron is set a few years after most of the countries that used to make up the Empire of Galifar have finally made an uneasy peace following one of them being destroyed overnight in mysterious circumstances. Galifar left behind standardized coinage and (now unenforceable) agreement of checks and balances on the Dragonmark Houses, though railways, major roads, the primary language, and many other institutions are attributed to the still extant Dragonmark Houses. Since the Five Nations can't move militarily without fear of breaking the truce, Sealed Evil in A Can and other international threats must be solved by the player characters.
 * Points of Light is set a hundred years after the fall of the Empire of Nerath. Now the mightiest factions friendly to humanity left are mere city states who struggle to project power beyond their walls and hire mercenaries to deal with all manner of external issue. Nerath has left behind vast ruins filled with treasure and a single language, and is presumably responsible for the standardized gold pieces as well.

Video Games

 * The Calradic Empire of Mount & Blade has been gone for a few hundred years leaving behind several factions who all claim to have a historical right to the rest of the former empire (and thus reason to wage on/off war with their neighbors). Naturally it's up to the player to do something about this. The prequel, Bannerlord, is set just as the empire has split from a Succession Crisis and its former tributaries have broken off.

Real Life
Eras that count when used for Historical Fiction
 * Post Han-Dynasty China, made famous by Romance of the Three Kingdoms and its many derivatives.
 * The Sengoku Period of Japanese history.
 * The Low Middle Ages