It rises on the side of the Cathedral and we can suppose that the latter was built by bishop Ursus, in the first decades of the 5^th century. It is also called "Neoniano" from bishop Neon who brought substantial renewal.

It is a big octagonal prism of ancient bricks and the original level is about three meters below the current floor.

All the surface of the inside walls is richly decorated with stucco, inlays of marbles and mosaics. 

Click on the image and visit the Baptistery