This Romanesque cathedral has two apses, each flanked by two spiral staircase towers. The west chancel, with its double tier of Rhenish stacked galleries, is one of the finest Romanesque creations in Germany. Inside, note the high altar by Balthazar Neumann, the transept crossing and its Rhenish cupola, the Gothic sculptures in the north aisle and the tombs of relations of Emperor Conrad II (beneath the chancel).