Originally of gothic style, it was built in two phases between 1304 and 1458, taking up a consistent portion of the district and of the ancient parish of Santo Stefano del Castellare. It was reconstructed by Carlo Maderno in 1632 after a succession of collapses. Inside only part of its former, extremely rich patrimony, dispersed after the Napoleonic requisitions and the post unity acquisitions by the state. It mainly consists of works dating to the XVII and XVIII Century, but there are also frescos of the XIV-XV Century in the transept and the chapel dedicated to Santa Caterina. Precious is the funereal monument to Pope Benedict XI (XIV Century).