Basilica di Santa Maria in Trastevere

Tradition dates the founding of a church on this site to the early 3rd century under Pope Callixtus I, and later legend holds that a spring of oil miraculously flowed from the ground here on the day of Christ's birth — a story medieval Romans used to claim this was the first place in the city where Christian worship was openly and legally practised, predating the Roman Empire's official conversion to Christianity by roughly a century. Whether or not the legend holds up historically, the church that exists today, largely rebuilt under Pope Innocent II around 1140, is genuinely one of Rome's oldest surviving churches in continuous use.

The basilica's defining feature is its façade and apse mosaics, dazzling gold-ground work from the 12th and late 13th centuries respectively. The façade mosaic shows the Virgin Mary enthroned, flanked by ten women bearing lamps — a striking, almost jewel-like composition visible from the piazza outside even before entering. Inside, the apse mosaic cycle, largely the work of Pietro Cavallini around 1291, depicts scenes from the Life of the Virgin with a naturalism and warmth that art historians consider a crucial bridge between Byzantine-influenced medieval art and the emerging humanism of Giotto and the early Renaissance.