The news about the construction of the Church are from before 1198, therefore, the building should be the early Christian, as evidenced by the lions on the portal. In 1292 the Cchurch was transformed into a Gothic style, with a work that lasted over time and saw the work by architects John Santucci and his nephew Bartolo. The interior has three naves of equal height, each with an entrance from the facade and gates decorated with bas-reliefs of saints, biblical prophets and plant motifs. From the two aisles are followed thirteen chapels with frescoes and statues, among which the fresco of the "Madonna with Child and Two Angels", by Masolino da Panicale. In the apse is the choir from 1590 by Antonio Maffei of Gubbio. In the crypt under the altar is the mausoleum containing the remains of St. Cassiano. Initially, the chapel was to Jacopone of Todi, who had been buried in the sacristy. In front of the Cchurch promises a square with sloping garden and in which branch of flights of stairs to access. Adjacent to the Church is the fifteenth century bell tower, whose summit offers a wonderful view of the city and the valley.