In ancient Greece, an independent city and its surrounding region under a unified government. A polis might originate from the natural divisions of mountains and sea and from local tribal and cult divisions. Usually the town was walled and contained a citadel on raised ground (acropolis) and a marketplace (agora). Government was centred in the town; usually there was an assembly of citizens, a council, and magistrates. Ideally, all citizens participated in the government and in the cults, as well as in defense and economy. Women, minors, metics, and slaves were not citizens. Hellenism spread many of the institutions into the Middle East. See alsoAthens; city-state; Sparta; Thebes.