http://www.mtwashingtonbicyclehillclimb.org/mwarbh/page.cfm/About-This-RacePerhaps the toughest hill climb in the world. 7.6 miles at 12% grade, extended sections at 18% and the last yards at 22%. You can only cycle up it, you cannot cycle down (need proof that you have a ride in a car down before you can go up). Limited to 600 cyclists and sellout fast.
I drove this last year and it was scarier going up than driving down! People who are afraid of heights or not good drivers, do not drive on this road!