4 boulevard du Palais
La Sainte-Chapelle, or Holy Chapel, is the lone surviving building of the Capetian Royal Palace in the heart of Paris. It was originally built to house King Louis IX's collection of religious relics, such as the Crown of Thorns.
The brightly colored, vaulted ceilings within are some of the most beautiful and vibrant in all of Gothic architecture, and many of the stained glass windows of the chapel are 13th-century originals. This chapel inspired many imitators in the city, so be sure to check out the original on the Ile de la Cite.