In the Norman style, it suffered severe damage due to the earthquake of 1908 and the bombings of 1943. On the main facade, there are three portals, with the central one framed by columns topped with statues. Above, there is an architrave containing the statue of the Madonna with Child, and in the background, the figure of Christ among the four evangelists. Following that, there is a pinnacle with the Virgin crowned by Christ, and it is all topped by the figure of the blessing Christ.
Inside, there are three naves and a double row of 13 columns. Of notable importance are the richly inlaid main altar made of precious stones, which contains the painting of the Madonna della Lettera, the most important pipe organ in Italy, mosaics, funerary monuments, and statues of saints, including the Saint John the Baptist by Gagini.