In spite of a restoration almost amounting to renewal, the Sainte-Chapelle is still one of the most beautiful buildings in France. It was the reception of the Crown of Thorn from Jean de Brienne, Emperor of Constantinople, and a great portion of the True Cross from his successor Beaudoin,which made Saint-Louis determine to build a shrine worthy to contain them. Pierre de Montereau was employed as an architect, and the Sainte Chapelle, begun in 1242, was finished in 1247.
The two stories of the building, forming two chapels, were consecrated April 25, 1248, the upper under the title of Sainte Couronne and Sainte Croix; the lower under that of Sainte Marie. No external stair leads to the upper chapel, because it was the royal oratory opening from the palace. The upper chapel is entered by a gothic double portal. It is a mass of gilding, and is harmonious in color from the fifteen stained windows, which, as far as possible, are restorations of the old windows mutilated during and after the Revolution. Under the windows of the fourth bay on either side the nave are niches, containing the places of honour reserved for the Queens and Kings. In the fifth bay, a grille permitted Louis XI. to assist unseen at mass. One of the little tourelles at the sides of the shrine, that on the north, still contains the actual wooden stair which was ascended by Saint Louis when he went to take from its tabernacle the Crown of Thorns, which he, and he alone, was permitted to exhibit to the people below, through a large pane of glass.