To the south of the cloister is the chapel of St. John with its unobtrusive exterior, originally probably the house chapel of the bishop, later the baptistery. It has two floors and is decorated with precious frescoes from the romanesque (1250), early (around 1320) and high gothic (1st century of the 15th century). According to tradition, the Synod of Bishops met here in 1048, which Emperor Henry IV had convened in the course of the investiture conflict in order to have Pope Gregory VII deposed and elevate Clement III to the position of antipope