North of Place des Cordeliers is the former Abbaye de St-Germain, which stands parallel to the cathedral some 300 yards away. The church's earliest aboveground section is the 12th-century Romanesque bell tower, but the extensive underground crypt was inaugurated by Charles the Bald in 859 and contains its original Carolingian frescoes and Ionic capitals. It's the only monument of its kind in Europe—a layout retaining the plan of the long-gone church built above it—and was a place of pilgrimage until Huguenots burned the remains of its namesake, a Gallo-Roman governor and bishop of Auxerre, in the 16th century.
Pl. St-Germain, Auxerre, 89000, France