The Benedictine abbey-church retains elements from the Romanesque period, most notably in St Catherine's Chapel), but it was extensively remodelled in the 17C and 18C. At the entrance, a wrought-iron grille separates the porch from the nave, whose simplicity highlights the elegance of its Rococo decoration. Frescoes depict saints' lives. The St Peter's Museum, incorporated in the Domquartier cultural complex, gives an overview of 1 300 years of the abbey church's history.