The church has an upper gallery, originally used by women and now the nun's choir. In this gallery, you can see a fresco by Pietro Cavallini (1250-1330), The Last Judgement painted, c. 1293, considered to be his masterpiece. This painting is considered a turning point in the history of art, as it was one of the main inspirations for Renaissance art and thus marks the end of the Byzantine style. It's also the only surviving painting by Pietro Cavallini . It was covered up by a wall for several centuries, until it was rediscovered in 1900. As the nuns live strictly enclosed, the gallery is closed to the public most of the time.