This brooding 4th-century church, rebuilt as a fortified convent after it was destroyed during the 1084 Norman sack of Rome, is dedicated to four Christian sculptors who were killed by Diocletian for refusing to make a statue of a pagan god. As a result, it’s still revered by stone-cutters and masons. The most famous feature is the Cappella di San Silvestro and its well-preserved 13th-century frescoes depicting the story of the Donation of Constantine, a famous document by which Constantine ceded control of Rome and the Western Roman Empire to the papacy.

Also of interest are the beautiful 13th-century cloisters off the northern aisle (ring the bell for admission).