This hilltop Carolingian collegiate church replaced a funerary church built by St Ursmer c 713. It was enlarged in the 11C, so the chancel, crypt, porch and Mosan-type west tower are Romanesque. The tower above the transept crossing was added in the 19C. The crypt, with pillars reworked in the 16C, houses the tombs of St Ursmer and St Erme.