Massive skate park for road bicycles
The Flash 9.0.0 plugin or higher is required to view content on this page, but was not detected on your browser.
I am always on the lookout for natural half pipes: streets that go down a steep hill and then straight back up another hill. For roadboarding and bicycling, it's my favorite; going up and down, up and down, with minimal effort.
So the idea is to build a massive park, initially one half pipe, that was maybe 100 feet long, 30 feet high. I don't know the physics, but you get the idea, insane speed. Not neccesarily going airborn, just tracing beautiful weightless arcs, 25 feet up, on a well tuned racing
Analogues of all the various ramps, bowls, rails, jumps, existing in skateparks could be made. And many vehicles could be used, go-karts, road boards, dirt bikes, sleds... The idea could be extended further, skate parks for cars, and that's probably far enough.
A cheap alternative would be for someone to start a website mapping natural half pipes. I know of a lot of mediocre ones, and one ok one in Richland Washington...