It's called the Narcisse Snake Dens and you can find them in Manitoba, Canada. Which is way too close for my comfort to Michigan.
Every year about 70,000 garter snakes get together to get it on. In case you don't know my biggest fear in the world, I'm talking more than burning alive, drowning, falling out of a plane etc. IT'S SNAKES.
If you are like me, don't watch this video. If you're crazy (as I assume snake lovers are) go ahead and enjoy.