The beauty of this cathedral resides in its architectural unity. Most of the building was completed in a short time (1095-1133); and despite later additions the whole remains harmonious. The cathedral dominates the palace square, the university buildings surrounding it and the castle. The solemn majesty of the nave is enhanced by the two 13C west towers, the 15C central tower (66m) and, to the east, the flying buttresses supporting the Nine Altars Chapel.