While its facade has been left unfinished, the church has a wide and monumental interior. The transept houses important tombs dating from the Renaissance period, while the presbytery, raised above the crypt, is the work of the Tuscan sculptor Giuliani Vangi and dates from 1997.
Ancient records bear witness to the existence of an Early Christian cathedral, which stood on the site of the space in front of the present building. The subsequent church on the site was consecrated in 1075 but then damaged by an earthquake in 1117. In the sixteenth century a competition was held for designs to expand the cathedral and the winner was Michelangelo himself; however, the actual work was overseen by Andrea da Valle, who made substantial changes to the original project designs. The Cathedral was only completed in 1754, even if its grandiose facade, which Frigimelica designed with three main doorways and two rose windows, was never finished; it – along with the cupola – would then be seriously damaged by shelling in 1917-18, during the First World War.
The Latin-cross interior is a harmonious, light-filled, space comprising a central nave and side aisles divided by pilasters. The new presbytery brings the high altar closer towards the nave, thus affording more focus on the sixteenth-century choir, which is adorned with statues of the city’s patron saints by Giuliano Vangi. Down in the crypt one can see the St. Daniel Altar and the small chapel where many of the city’s bishops are buried. Tradition has it that the icon of the Madonna and Child in the south transept once belonged to Francesco Petrarch, who was known for his Marian devotion; he himself believed that the work had been painted by Giotto.