Acropolis
Acropolis (Gr. akros, top, polis, city), literally the upper part of a town. For purposes of defence early settlers naturally chose elevated ground, frequently a hill with precipitous sides, and these early citadels became in many parts of the world the nuclei of large cities which grew up on the surrounding lower ground.
The word "Acropolis", though Greek in origin and associated primarily with Greek cities (Athens, Argos, Thebes, and Corinth with its Acrocorinth), may be applied generically to all such citadels (Rome, Jerusalem, Celtic Bratislava, many in Asia Minor, or even Castle Hill at Edinburgh).
The most famous example of the kind is the Acropolis of Athens, which, by reason of its historical associations and the famous buildings erected upon it, is generally known without qualification as simply "The Acropolis".
Because of its classical Greco-Roman style, the ruins of Mission San Juan Capistrano's "Great Stone Church" (in California, United States) have been dubbed the "American Acropolis".
Other parts of the world developed other names for the high citadel or alcázar, which often reinforced a naturally strong site. In Central Italy, many small rural communes still cluster at the base of a fortified habitation known as "La Rocca" of the commune.
The term Acropolis is also used to described the central complex of overlapping structures, such as plazas and pyramids, in many Mayan cities, including Tikal and Copán.
 

From: www.wikipedia.org