The cathedral, founded in 1030 and remodelled at the end of the 11C, is a Romanesque basilica with four towers and two domes and a UNESCO World Heritage Site. The transept is a masterpiece of harmony and balance. The chapel of the Holy Sacrament houses two 15C bas-relief sculptures. The Romanesque crypt, beneath the chancel and transept, consists of a network of groined Romanesque vaulting. Four Holy Roman Emperors and four German Kings are buried in the Emperors' Crypt.