Amongst the archeological sites worth visiting in the area around Ansedonia, Cosa is particularly interesting, an ancient city abandoned in the 14th century. There are ruins of the massive walls, Roman forum and Temple of Jupiter. Nearby, you can see Villa Settefinestre, dating to the 1st century BCE, even if it was modified in the 15th century.
The walls around Cosa, built in the 3rd century BCE, were renovated by the Aldobrandeschi Counts in the 11th century before being abandoned once again. The walls were restored to their ancient glory following a long restoration at the end of the 20th century.
In the same area, you can also find the Tagliata Etrusca, an impressive work of engineering dating to the Etruscan-Roman period. This canal cut into the rock face runs along the coast to the south-east of the promontory and was designed to impede the port from silting by creating a system of counter-currents coming from the sea and the emissary of the nearby Lake Burano. Lastly, you can learn about the Spacco della Regina while you’re here, a large opening in the promontory that runs the length of some artificially-dug tunnels.
The itinerary then continues over the border into Lazio, heading in the direction of Vulci, an ancient Etruscan city located on a chalky platform on the right bank of the Fiora. Vulci was one of the largest city-states in Etruria, with a strong maritime and commercial industry with Greece and Asia, as shown by the lavish funerary goods discovered in the nearby necropolises, today conserved in museums all over the world.