The cathedral was founded in 1030 and remodelled at the end of the 11C. It is a Romanesque basilica with four towers and two domes. The transept is a masterpiece of harmony and balance. The chapel of the Holy Sacrament houses two 15C bas-relief sculptures. Above the baptistry stands the chapel of St. Catherine. The Romanesque crypt consists of a network of groined Romanesque vaulting. Four Holy Roman Emperors and four German Kings are buried in the impressive Royal Vault.