The chapel was named after Bishop Giovanni Montemirabile (†1479) and it was transformed into the baptistery of the basilica in 1561. The most valuable works of art in the chapel are the aediculae of the baptismal font and the font of the holy oil. These were assembled in 1657 from the 15th-century fragments of a demolished monument which had been created by the Bregno workshop. The tomb of Cardinal Antoniotto Pallavicini on the left wall was made by the same workshop in 1501.