The cathedral at Ely was built by William the Conqueror to show his devotion to his religion. The Norman tower collapsed in 1322, but instead of rebuilding a tower in the same style (as seen at Winchester) the medieval masons constructed an eight sided lantern. The lantern is decorated with stained glass windows, lighting the centre of the cathedral. It is supported by heavy oak beams and tree trunks, which are disguised by stone vaulting. It is still not understood how the lantern was constructed nearly seven hundred years ago.