If one is ever near you, GO!!! Its totally worth the experience, there are crazy amounts of people all there to have a good time. For the main tracks, they use refrigerated lines under the track and add water on top. For this ski-hill track, they just spray water, let it freeze, and repeat many, many times until the snow itself is a hard (and bumpy compared to a man made track) surface. And yes, these guys are insane, I wouldn't even go down these tracks on a sled.