This church's curious shape (an octagon covered by a cupola) is inspired by the cathedral in Aix-la-Chapelle. The church was built by the prince-bishop Notger in the late 10C. Its main building was raised in about 1200 and its nave built in the 18C. Inside the church, the rotunda and choir have been decorated in neo-Classical style. The cloister, added in the 16C, was modified in the 18C. The church's southern gallery still has a very nice 16C vault.