The Sainte-Chapelle, or ‘Holy Chapel’, was built inside the Royal Palace on Paris’ Ile de la Cité around 1240 by Louis IX to house relics from the crucifixion. From the outside it looks like another Gothic cathedral, but inside it hides a colourful secret. The lower chapel is richly decorated in blues, reds and golds, painted with intricate stars on the ceiling and fleur-de-lis symbols. And this was only the servant’s chapel. After climbing up a narrow spiral staircase you emerge into the upper chapel.