To quote Wikipedia, the Conciergerie is “a former royal palace and prison”, located in the heart of Paris (for fans of French history; this is where Marie Antoinette and Charlotte Corday, among others, were imprisoned). Even though it’s close to all these other places tourists love (the Louvre, Notre-Dame, etc) it was actually very quiet when we visited. I absolutely loved it; it was full of history (make sure to bring your reading glasses) and had a very unique atmosphere. While it wasn’t our most photogenic stop, I keep a really good memory of our visit there.