This was such a cool thing to do in Paris!! I highly recommend it to anyone looking to learn more about the dark history there. It’s eerie but so interesting!! It’s a little tricky, but definitely try to buy your tickets online before your trip. I wrote a step by step guide on how to do this on my blog. The site is entirely in French with no option for translation so it’s really hard to navigate. Send me a message if you want more info!