The Mosaics of Monreale Cathedral form the building's main internal feature and cover 6,500 m2. They are made of glass tesserae and were executed in Byzantine style between the late 12th and the mid-13th centuries by both local and Venetian masters. With the exception of a high dado, made of marble slabs with bands of mosaic between them, the whole interior surface of the walls, including soffits and jambs of all the arches, is covered with minute mosaic-pictures in bright colors on a gold ground. The mosaic pictures, depicting stories from both the Old and New Testament, are arranged in tiers, divided by horizontal and vertical bands.