Chiusi, whose name derives from the Latin Clusium, that is a naturalization of the Etruscan name Clevsin, experienced its greatest splendour under the legendary king Porsenna. Very significant finds from archaeological digs that are still successfully under way may be seen at the National Etruscan Archaeological Museum.
During the Roman domination Chiusi had a great importance because the ancient Roman "Via Cassia" passed through its territory thus allowing the increasing of a flourishing economic activity. The building of a fortress, whose remains are still visible today, goes back to that time.
Christianity spread very swiftly in these places, as borne out by the Catacombs of Santa Mustiola and of Santa Caterina. Over and above the catacombs you can also see the so-called Labirinto di Porsenna, an intricate network of underground passages leading to a cistern dating to the 1st century AD.
As a result of the foregoing, but also of its considerable natural attractions, Chiusi is developing its capacity for tourism. An important element is the lake of Chiusi, downstream of the town, which offers the possibility of sport fishing and birdwatching.