Sainte-Chapelle, Paris

A royal chapel built in the 1240s by King Louis IX to house relics of the Crown of Thorns, hidden inside the Palais de Justice on the Île de la Cité. The upper chapel has walls almost entirely of 13th-century stained glass, 15 windows showing over 1,100 Bible scenes, glowing like jewels on a sunny day.

There's a security check for the law courts, so book a timed ticket online. A combined ticket includes the Conciergerie next door, the prison where Marie Antoinette was held. Evening concerts are held in the chapel.