King Louis IX commissioned the Sainte-Chapelle, in the Palais de la Cité, to house his Passion relics, including the Crown of Thorns. Construction began after 1238, and the chapel was consecrated on April 26, 1248. Pierre de Montreuil was long assumed to be the architect, but modern scholarship rejects this.
The design is Rayonnant Gothic, conveying weightlessness and a strong upward emphasis. Two levels of equal size served different groups: courtiers, servants and soldiers used the lower chapel, while the upper chapel was reserved for royalty. The building is 118 feet (36 m) long, 56 feet (17 m) wide and 139 feet (42.5 m) high. The upper chapel holds fifteen great stained-glass windows and a later rose window.
The French Revolution damaged the chapel and scattered its relics, and restoration began in 1840. Some relics survive in the treasury of Notre-Dame. The chapel is now run as a museum by the Centre des monuments nationaux.

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