The chapter on Greeks, Lucanians and Romans at Poseidonia/Paestum (South Italy) presents a specific aspect of the problem: the definition of cultural identities in the southern part of the Italian Peninsula which developed concurrently with the emergence and rise of the Roman Republic, and eventually became part of the Augustan tota Italia, an “imagined community” in which all the disparate local histories and geographies could be unified. In the light of the most recent debate on cultural interaction and identity in the archaeological record, the site of Poseidonia/Paestum provides us with an excellent case study on phenomena of cultural contact and cultural change in the southern part of the Italian Peninsula during the second half of the first millennium. Closely related to the cultural changes discussed is a notorious passage on the history of early Italy by Aristoxenus referring to Poseidonia/Paestum.