Greece is a mountainous land of peninsulas and thousands of islands where the Minoans and Mycenaeans established early civilizations. The Greeks developed a polytheistic religion and cultural traditions like drama and the Olympics. City-states called poleis emerged, each centered around an acropolis and temple. Athens and Sparta grew to dominate as rival powers - Athens established a direct democracy while Sparta focused on its powerful military. The Persian Wars united the Greeks against invasion, and a Golden Age followed for Athens under Pericles' leadership, but the Peloponnesian War between Athens and Sparta weakened Greece.