The late 15th-century Baptistery, formerly the church of San Lorenzo and later of the Blessed Virgin of the Rosary, has a wide 17th-century portico to the south with a balustrade. The original entrance is at the east end, a stone doorway with “candelabra” decoration (15th century). Inside the church is a monolithic font from 1399 with a wooden cover surmounted by a sculpture of John the Baptist. At a lower level are the remains of an early Christian apse and a Roman hypocaust.