This building stands on the foundations of a Roman temple and is typical of late Ottonian architecture. The trefoil shape of the choir and transept is the oldes of its kind in Cologne. The church is also worth the detour for its crypt that is the second largest after the crypt of Spire cathedral's. Inside, admire the Renaissance rood screen and the two funerary steles by Plektrudis, wife of Pepin of Herstal. Also don't miss the Romanesque wooden doors.