The Fortress has squared shape and was built by order of Pope Innocenzo VI and Cardinal Albornoz to give Orvieto a more strong defense, but mainly to prove again the power of the Church over Orvieto. It was projected by Ugolino di Montemarte in 1364.

Now it is a public park with gardens and monumental trees. In summer concerts and popular festivals are held here. From the ramparts visitors can enjoy a beautiful view over the valley. Next to the fortress is the worldwide famous Pozzo di San Patrizio (St. Patrick's well) and the remains of the Etruscan Temple of Belvedere.