The Sainte Chapelle was (and is) a beautiful little church or chapel in France, on the island in the middle of the city of Paris. King Louis IX, also known as Saint Louis, and his mother, Queen Blanche of Castile, built it between 1241 and 1248 AD AD (before Louis left on the Seventh Crusade).

King Louis, showing off how rich he was, bought the Crown of Thorns and a piece of the Cross from the Byzantine Emperor, Baldwin III. According to Emperor Baldwin, this was the actual Crown of Thorns that Jesus wore on his head during the Crucifixion. Louis paid a fortune for this sacred crown.

Sainte Chapelle window
When the piece of the Cross and the Crown of Thorns arrived at Louis' palace (the old Roman fort in Paris), Louis wanted to build a chapel to keep his crown in (just as earlier rulers in India built stupas to keep relics of the Buddha in). Louis wanted a beautiful chapel that would be worthy of his sacred crown that had touched the skin of Jesus.