In 1507 Pope Julius II resolved the anomaly and transferred the bishop's seat from the sub-urban church of San Vincenzo.
The appearance of the original medieval church is mostly hidden by later additions, such as the 18th century barrel vaulted ceiling in the nave, which was repainted in the late 19th century by the local artist Giovanni Brunacci; in the same period the oval windows, the triumphal arch and the pavement were also added or remade.
The oldest elements visible are in the Romanesque façade - a pier with capital, and small columns at the corners, and part of the large arcade.
Artworks in the interior include an Adoration of the Shepherds by Pietro da Cortona and assistants (c. 1663), a Consecration of the Church of the Holy Saviour by Andrea Commodi (1607, brought here in the late 18th century) and a Descent of the Holy Spirit by Tommaso Bernabei (1528-1529).
The town's Diocesan Museum houses works formerly in the cathedral, including Pietro Lorenzetti's Maestà (before 1320), and a tapestry and a reliquary from the period of the Renaissance.