Hidden away in the Palais de la Justice, Sainte-Chapelle is a jewel of flamboyant Gothic architecture built to serve Louis IX (St. Louis) in the 13th century. Its soaring stain-glass windows are some of the most beautiful in the world. It recently completed seven years of renovation. Open daily except New Year's Day, Christmas and May 1. Adult admission 8,50 €, under 18 free with family. Admission is free when attending concerts that are occasionally held at night.