The cathedral was built in the eleventh century but extensively altered in later centuries. The figurative and decorative motifs of the three naves date from the late nineteenth century. The fresco of the main chapel, dated 1723, is by Francesco Porro. A remarkable feature if the fifteenth century Annunciation painted in the chapel of St.John. The crypt is dedicated to Saint’Antonio Maria Gianelli, bishop of Bobbio from 1838 to 1846.