When I was a youngin, I would ride my bike down Puritas Hill which is in the West Park Neighborhood of Cleveland. It's a pretty steep hill but by no means was a mountain. I tried roller-blading down Puritas Hill and it didn't end well for my knees and elbows and other assorted body parts.
This dude hopped on a skateboard and flew down a mountain in Switzerland reaching speeds of 70mph which is of course crazy. It did make for a cool video.