This castle is situated along the Gualdo Cattaneo-Todi motorway, at 500 meters above sea level. It was built in the 14th century to defend the population from attacks. The origins of this place are very ancient (1st century a.c.): the Romans called it "loco petroso" after its caves rich in chalky rocks and travertine. The castle was built following a traditional typological scheme with square plan and using the local rocks. It took its name after Terenziano, the firs bishop of Todi, beheaded with Flacco, priest of the Collegio degli Augustali, by Emperor Hadrian. The night following their death, some Christian women collected the two bodies and brought them to the Petroso plateau, which from that moment on would be called San Terenziano. The castle was involved in the political and military events of Todi, and some lords lived in it; a house Inside the walls still bears an emblem of the Atti on one of its architraves; it was then property of the town of Todi and it was part of the Colle, Valle and Cammucia districts. In 1354 it came under attack by some military operations of Father Moriale D'Albarno, who, after putting attacking the towns of Spello and of Beroide and after robbing the territories of Trevi and Montefalco, moved towards Todi. Il Moriale, Provencal knight and captain of the Great Company, after the attack in San Terenziano was convinced by his brothers to move to Rome, where Cola di Rienzo had just returned. Unfairly accused by the court, he was arrested together with his companions and beheaded on 29 October 1345. In 1440, after the destruction of the Castelvecchio Castle by Francis I Sforza, the priors of Todi gave the bell of the church to the community of San Terenziano as a gift.