Basilica di Santa Maria in Trastevere
Tradition holds that a basilica was founded on this spot by Pope Callixtus I in the 220s AD, which would make it one of the very first places in Rome where Christian worship was openly tolerated. Legend ties the site to the "fons olei", a miraculous spring of oil said to have burst from the ground here on the night of Christ's birth — an event the church still commemorates with an inscription on the floor.