From Wikipedia

 

HISTORY

 

Paestum was a major ancient Greek city on the coast of the Tyrrhenian Sea in Magna Graecia. After its foundation by Greek colonists under the name of Poseidonia (Ancient Greek: Ποσειδωνία) it was eventually conquered by the Lucanians and later the Romans. The Lucanians renamed it to Paistos and the Romans gave the city its current name.The ruins of Paestum are notable for their three ancient Greek temples which are in a very good state of preservation. Today the remains of the city are found in the modern frazione of the same name, which is part of the comune of Capaccio in the Province of Salerno, Campania, Italy.

 

FOUNDATION

 

According to Strabo the city was founded as Poseidonia by Greek Achaeans from Sybaris. The colonists had built fortifications close to the sea, but then decided to found the city further inland at a higher elevation. The fortifications might have been built to the south of Poseidonia on the promontory where Agropoli is now. According to the historical tradition the sanctuary to Poseidon was located there, after which the city would have been named. The date of Poseidonia's founding is not given by ancient sources, but the archaeological evidence gives a date of approximately 600 BC.

Alternatively, the Sybarites may in fact have been Troezenians. Aristotle wrote that a group of Troezenians was expelled from Sybaris by the Achaeans after their joint founding of that city. Gaius Julius Solinus calls Paestum a Dorian colony and Strabo mentions that Troezen was once called Poseidonia. As a consequence it has been argued that Paestum was founded by the Troezenians referred to by Aristotle. Another hypothesis is that the Sybarites were aided by Dorians in their founding of Poseidonia.