This wonderful Gothic-style edifice (12C and 13C) was completed in the 16C. It gives an idea of the importance the Duke of Dol's status at that time: on the south side, you will notice the large porch (14C); inside, the nave is almost 100m long (and the vaults almost 21m high). In the chancel, admire the superb great stained-glass window with medallions, the 80 stalls (14C) and episcopal throne (16C). The tomb in the left arm is a rare vestige of the Italian Renaissance in Brittany.