Baptistery is located next to Cathedral of the city. It is 34 meters high and has a diameter of 20:50 meters; the plant of the building is octagonal, with reference to eternity. It was started in 1167 and is characterized by a cover made of marble on some sides, alternating with exposed bricks. The light penetrates inside by a double set of double windows overlapping and the lamp at the top of the dome. Baptistry houses a sixteenth-century baptismal font, which dominates in the interior area with the large cistern also octagonal, by Lorenzo Trotti (1527).