The Church of San Giovanni in Fonte is famous for its 12th-century Romanesque octagonal baptistery by the sculptor Maestro Brioloto. It can be accessed from the door under the left pipe organ of the Duomo and is dedicated to St. John the Baptist.
Dating back to the Lombard period, it was completely rebuilt after the disastrous earthquake of 1117.
Along its three aisles with apse, the capitals of the columns dates back to the 7th century, while the frescoes to the 14th century. It houses major paintings, such as the Baptism of Christ by Paolo Farinati.
However, its most important work of art is the Baptistery, a monolithic red marble tank about 3 metres large; on the eight faces of the source, delimited by elegant archery frames, we find marvellous bas-reliefs depicting the life of Christ.