This set of buildings developed in the late medieval period in an area once used as a cemetery. The original church erected by Sant’Orso had a single nave but Bishop Anselmo added two more naves in the 10th-11th centuries. Inside there are 15th Century frescoes in the presbytery and the apse. The ceiling of the central nave conceals another, containing a fresco cycle depicting the Episodes of the life of Christ, martyrs and saints. The wooden choir stall is worthy of note with its showy 15th Century Gothic style.