The building is the result of numerous restorations over the course of the centuries, starting as a primitive Longobard structure which was first recorded in 650. The current façade is from 1866 (nineteenth century).
It is not considered a proper cathedral even by the local residents, but it is still worth visiting for the extremely interesting works of art on display inside: the "Martirio di San Giovanni Vescovo" (Martyrdom of St John the Bishop), a canvas by G.B. Tiepolo (1743), set in the choir, behind the high altar; the "Madonna col Bambino e i santi" (Madonna with Child and Saints), by G.B. Moroni (1576), placed on the first altar on the left; the "Cristo Crocifisso con la Madonna e i santi" (Christ Crucified with the Madonna and the Saints), by G.B. Cavagna (second half of the sixteenth century), on the right-hand side; the marble bas-reliefs by Andrea Fantoni representing the Seven Sorrows of Mary (second half of the seventeenth century), in the left transept; the wooden choir, an truly remarkable work from the seventeenth century: the 44 stalls are attributed to G.C. Santz, while the bishop's throne, at the centre, is by Andrea Fantoni.