to the sacristy on the left lateral traverse. Since it could not have a window, it was decorated in the 13th century with a mural of the Annunciation. This was rediscovered during the 19th century work, and restored by Steinheil. Upper Chapel The upper chapel is reached by narrow stairways in the towers from lower level. The structure is simple; a rectangle , with four traverses and a apse at the east end with seven bays of windows. The most striking features are the walls, which appear to be almost entirely made of stained glass; a total of of glass, not counting the rose window at the west end. This was a clever illusion created by the master builder; each vertical support of the windows is composed of seven slender columns, which disguise their full thickness. In addition, the walls and windows are braced on the exterior by two belts of iron chain, one at the mid-level of the bays and the other at the top of the lancets; these are hidden behind the bars holding the stained glass. Additional metal supports are hidden under the eaves of the roof to brace the windows against the wind or other stress. Furthermore, the windows of the nave are slightly higher than the windows in the apse ( compared with ), making the chapel appear longer than it actually is. There are two small alcoves set into the walls on the third traverse of the chapel, with archivolts or arches richly decorated above with painting and sculpture of angels. These were the places where the King and Queen worshipped during religious services; the King on the north side, the Queen on the south. Vaults of the upper chapel Stained glass The most famous features of the chapel, among the finest of their type in the world, are the fifteen great stained-glass windows in the nave and apse of the upper chapel, which date from the mid-13th century, as well as the later rose window (put in place in the 15th century). The stone wall surface is reduced to little more than a delicate framework. The thousands of small pieces of glass turn the walls into great screens of coloured light, largely deep blues and reds, which gradually change in intensity from hour to hour. Most of the windows were put into place between 1242 and 1248. The names of the glass artists