Dedicated to Saints Fermo and Rustico, early 6th century martyrs, the basilica was given to the Benedictines in the 10th century and completely rebuilt in Cluniac style, with three naves and apsidal transept, in the period 1065-1143.
Only the lower church, with a central nave supported by a row of columns, and notable remains of frescoes, dates back to the Romanesque period.
In the 13th century, the abbey complex passed to the Franciscans, who rebuilt the upper church and the bell tower in gothic style.
The modern bronze door by Luciano Minguzzi (1984-88) was fitted in 1997. Inside, as well as the wood ceiling in the form of a keel, there are frescoes by Altichiero, Turone, Martino and Stefano da Verona, and also the Brenzoni funeral monument, with its splendid Annunciation by Pisanello (1424-26).