This map illustrates the city-states of Classical Greece around 500 BCE, highlighting the rise of the polis system and the growing reach of Hellenic influence along the Mediterranean and Black Sea coasts. The period saw Athens and Sparta emerge as dominant powers, shaping the political and military balance of the Greek world and laying the groundwork for collective resistance to external threats, most notably the Persian Empire.

Following the Persian Wars (499–449 BCE), Athens spearheaded the creation of the Delian League (established in 478 BCE) as a defensive alliance against Persia. Originally a coalition of independent poleis contributing ships, men, or tribute, the league quickly evolved into a vehicle of Athenian hegemony, with its treasury moved from Delos to Athens in 454 BCE. Under the leadership of statesmen such as Pericles (reign after 461 BCE), Athens converted this alliance into an empire that projected Greek naval power across the Aegean. While fostering prosperity and cultural achievement in Athens, this dominance also sowed resentment among other poleis, setting the stage for the rivalries and conflicts that defined the Classical age.