There are churches with members, and then there are special chapels built as reliquaries, that is to house precious Christian relics. But that is not all in this case. This chapel in the heart of Paris is a tribute to King Louis IX, destined to become Saint Louis, he was so pious, and was raised by his mother to be that way. The supposed relics collected and housed in this chapel included the crown of thorns, and a piece of the true cross. Neither of these were likely even remotely historically authentic, and they continued to promote the practice of collecting relics by major Catholic Churches in Europe, which would attract pilgrims wanting healing or help. Born in April 1214 in Poisy and dying in 1270 in Carthage, this Louis reigned from the time he was 12 for 43 years. The most notable part of his legacy was having this chapel built, which, as I mentioned, has no pews, no regular clergy, but has one of the most spectacular collections of stained glass windows in the world, which is what makes it worth a visit. Louis spent half the annual income of the kingdom buying these relics from the ruler in Byzantium in 1241. Sadly, we do not know who the architect was that built this chapel, but Louis clearly had a major say in its design, including windows encompassing the entire Bible, and a rose window of the entire book of Revelation! But let the pictures tell the story. There is a downstairs chapel, and an upstairs chapel, and the latter is the one most worth seeing. 
This 2 chapels in one, one on top of the other, explains the odd vertical shape of this building. Here is the lay out of the upstairs windows,
And here is an explanation of the iconography.
This picture gives you a sense of the overall effect of the upstairs windows.
There is a second floor balcony one can walk out on, overlooking the city under the rose window.
The rose window is the most spectacular window and it faces the rising sun so it gets the most light in the morning.
Close ups are hard to come by due to the height of the window, but I gave it my best shot.
And here’s a close up of one of the other windows.
One could spend all day upstairs in this building until your neck breaks looking at these. beautiful high windows, but there is also a downstairs chapel worth some time as well.
The downstairs chapel is more of a shrine to St. Louis, the statue is of him.
Not every chapel has two stories, and two roses windows, but this one does. And it was well worth the return visit after 30 years away from Paris.
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