Paestum is the Roman name of the city. The original Greek name was Poseidonia.

Only a fraction of the original extension of the city has been excavated, just around the ancient city centre with the temples and public buildings. The major parts of the area is privately owned and has never been examined.

Paestum and the surrounding area is a UNESCO World Heritage site.

Poseidonia was founded around 600 BC, probably as a colony of Sybaris, which was a flourishing city on the Ionian Sea. The city was the northernmost Greek settlement in Italy, just 8 km from the River Sele that formed the borderline between Greek and Etruscan domination.

The city was originally located near the coastline, close to the mouth of a small stream. The closest harbours were at the mouth of the River Sele to the N. (where a Heraion, a sanctuary to Hera, has been found) and Agropolis 8 km to the S. It is likely that sailors hauled their boats onto the beach if had they not used the more distant anchorages north and south.

What the site lacked sea-wise it had towards the hinterland. The land was fertile, water was abundant and important inland trade routes connected the city to the Greeks cities to the south and to the Etruscan cities to the north. The city grew on a combination of agriculture and trade.