The façade of alternate layers of white and black marble appears of Romanesque style, but is almost entirely result of the 16th century and 1816-1855 restorations: of the originary buildings, it retains decorative parts including Evangelists' symbols. The plant is a Latin cross, with transept and apse. The interior has a nave with two aisles, parted by cruciform pilasters. The main artworks are a wondrously carved baptismal font from 1470-1474 and the Madonna delle Grazie by Matteo di Giovanni (1470).
The campanile (belfry tower) was finished in 1402, and restored in 1911.