Why Is Sainte-Chapelle on the Île de la Cité?

Sainte-Chapelle stands on the Île de la Cité, an island in the Seine. It sits right in the middle of Paris. In the 1st century BC, a tribe called the Parisii settled on this island, and the city took its name from them. As the birthplace of Paris, the island became an important district early on, and from the 6th century the Palais de la Cité, home to the kings of France, stood on this very spot.

In the 13th century, Louis IX wanted to build a private chapel in the courtyard of the palace. Why a king would want such a chapel will become clear as the tour goes on. Even before that, the palace already had a public chapel, the Chapel of Saint Michael. You can find evidence of it on the wall to the left of the entrance line, in the form of a commemorative plaque. The chapel disappeared when roads were widened during Paris's modernization, and only the plaque remains. It carries a map-like carving of the area where you're standing now.

Compare it with a modern map and it matches perfectly: the red area is Sainte-Chapelle and the blue is the Seine. You'll notice that the chapel is surrounded by buildings. In the past, they were all part of the Palais de la Cité. The palace no longer survives in full; instead, the remaining sections house judicial and administrative bodies such as the Paris courthouse and police headquarters. That is why security at the entrance is so thorough.