The Sainte-Chapelle (Holy Chapel) is a royal chapel found in the Palais de la Cité and is one of the oldest buildings still standing on the Île de la Cité - the island in the middle of the Seine. It once housed the most important relics of Christendom, including Christ’s Crown of Thorns, but is today mostly notable for its incredible architecture and amazing stained glass windows. Book a skip-the-line ticket and discover it for yourself!