Dans le Noir is a restaurant where you dine in absolute, total darkness; really, it's pitch black. The waitstaff — all of whom are blind — coach you through the experience and give you a taste of what it's like to be sightless for an evening. It's a great, fascinating, and very strange experience, and definitely worth trying.
The front bar area of Dans le Noir is lit normally, and there you can talk to the hostess, listen to an overview of what to expect, and discuss the menu. I recommend going with the surprise menu, so you can enjoy eating stuff that you can't see and trying to identify all the flavours and textures; it's harder than you'd think! The front area also has lockers where you can leave your coats, bags and your phones since it'd be nigh impossible to locate your affairs at the end of the meal in the pitch-black dining room, not to mention the danger of tripping on things in the dark.
When it's time to enter the dining room, a member the waitstaff escorts you through a heavy black curtain and into the dining room, and seats you at your table.
Once you're seated and your meals come out, you'll be given a bit of instruction by your server — using clock positions to indicate where things are on your plate — and a great method for pouring wine when you can't see: just bend one finger into your glass as you pour, and when the wine touches your fingertip, stop! It's amazing how nervewracking this is the first time you do it and then how completely natural it is by the third time. But I'd avoid wearing white, in any case!
Dans le Noir is pretty expensive but you're paying for the experience, not the meal, and the strangeness of the whole thing makes it worth doing once.