Greeks had lived in the central Mediterranean from at least the eighth century BC. Cities like Chalkis, Eretria, Corinth, and even Sparta established colonies in southern Italy (which the Romans would eventually call “great Greece”: magna Graecia) and Sicily. Yet Athens played no role in this early Hellenic expansion to the west. The Athenians, as we have seen, apparently spent the eighth and seventh centuries consolidating their unusual, direct control of the large territory of Attica. Although the Athenians would ultimately claim that Athens had launched the Ionian Greeks on their ancient colonization of the islands and Asia Minor, the early Athenians could claim to be metropolis (“mother city”) of no Greek state founded in historical times.

By the mid-fifth century this situation had changed. In the 440s Athens played the leading role in the foundation of the colony of Thurii in southern Italy. The colony was unusual. A number of cities provided colonists, and the settlement was to occupy the site of the ancient Greek city of Sybaris, infamous for its luxurious lifestyle (giving us the term “sybaritic”) and torn by factional battles that had led to the city's destruction. The Greek intellectual and town planner Hippodamus of Miletus apparently played a role in designing the layout of the new settlement (as he had apparently designed the Athenians’ Peiraeus harbor). A late authority reports that the philosopher Protagoras made laws for the new city.