Ancient Greece was made up of independent city-states called poleis, each with an acropolis fortress on a hill. Greeks shared a common pantheon of gods and a panhellenic culture. The agora was a central marketplace and gathering place. Citizens had rights and protections within their polis, while foreign residents called metics paid for rights to live there. Early forms of government included aristocracies ruled by elites and oligarchies ruled by a few, which sometimes became oppressive tyrannies ruled by a single tyrant. Later, democracy developed where people directly governed or elected representatives to govern. Spartan society trained citizens through their agoge system to serve as hoplites in the famous phalanx