On the summit of the rocky promontory above the fancy villas of Ansedonia is the archaeological park of Cosa, founded by the Romans in 273 BC on the site of an ancient Etruscan settlement. It was built to ensure the Roman’s control of the region, to protect the nearby port of Orbetello, the coast, and inland, and was linked to Rome by road which served the large farms and granaries in the region.

Cosa itself, though, had an unfortunate history. Built with large imposing city walls, temples, temples, bathhouses, and many buildings, it was devastated by Hannibal during the Second Punic War, was rebuilt, sacked and abandoned again during the civil wars of the Roman republic, rebuilt and repopulated a third time by Augustus after an earthquake, and finally abandoned after a plague of mice and malaria. By AD 417 Cosa was deserted and in ruins.