The Baptistery of San Giovanni ad Fontes is a religious edifice in Lomello, Lombardy, northern Italy. An example of Romanesque-Lombard architecture, it is annexed to the basilica of Santa Maria Maggiore, another early Middle Ages structure.
The baptistery has a typical cross plan, but in the interior the central part forms an octagon, over which is a dome of the same shape. The interior is wholly plastered, and can be accessed from two portals. The baptistery has, on the east-west axis, an overall length of 16 m.
The main element is the baptismal font, dating to the 7th-8th centuries.[1]
The baptistery has an elevation of 13 m and is entirely built of brickworks, parts of which date to the 5th-6th centuries.[1] The dome is a later addition (c. 10th century), and was built using less precious materials.