I didn't know anything about the castle before we came, but it has an interesting history. It was built in 1150, and a bunch of French kings made improvements/were born/hung out there. Charles V used it has his study, and then later it was a porcelain factory, and even later than that a prison (there are still paintings on the walls done by prisoners). In 1791, a group of Revolutionaries planned on taking it down a la the Bastille, but no such luck. Then after that it was used to hold ammunition, and it's where Mata Hari was executed.
There's also a big ornate tomb to someone called the Duc d'Enghien, who was apparently executed there on false charges in 1804 under Napoleon. I don't really understand what happened, but apparently it was received badly by the public. He was eventually exhumed and they built him a big monument in the chapel. I read something about how the monument used to be somewhere else, and that it was a pain to get it in its current location.
(See? It takes up the entire room! I have no idea how they got it in there).
Anyway, it was fun to visit!
The view of the chapel from the castle.
There's also a lake nearby with boats that we're going to try to go to next week, rain permitting. We did make it to the Parc Floral, also right next door, because everyone needs a photo with big letters that spell out Paris!