Firmly anchored to the rock that supports it, it is on a site consecrated to prehistorical divinities. It is the best example of mediaeval architecture in the Montefeltro and one of the most important examples of Romanesque architecture in central Italy. Built in 1173, it includes the ruins of the early mediaeval cathedral dating from the 7th century when ancient Montefeltro, later San Leo, raised to the status of civitas, became seat of the new diocese. It faces east and the entrance is on one side, topped by the sculpted busts of St. Leo and St. Valentine, from the ancient church. The crypt once housed the sarcophagus containing the remains of St. Leo, although now only the 6th-century lid with inscription remains.