If you haven't seen it yet, check out the crazy downhill biking video that's making the rounds.  It's from the rider's point of view, and the course he's on is CRAZY steep.

Especially at the beginning, when he's on a thin trail with CLIFFS on both sides of it. 

Don't miss the part where he rides DOWN one of those cliffs at :24.  And the steepest part of the course is probably at 1:04.  Then he does a 360 at 1:38.