D
Ok, so this is technically not a hill, but it's pretty dope...
http://www.autoblog.com/2010/04/03/video-snowmobiles-iceland-and-70-foot-cliffs-you-guess-the-re/
http://www.autoblog.com/2010/04/03/video-snowmobiles-iceland-and-70-foot-cliffs-you-guess-the-re/