Get ready for the ultimate mountain bike challenge: 100 miles of rugged riding through the Colorado Rockies at serious elevation, starting at 10,152 feet and climbing as high as 12,424 feet. This event is designed to push only the most committed athletes to their limits, and you'll need serious determination to handle the extreme terrain and thin air—though the stunning scenery might just help you forget how hard you're working. By participating, you're supporting the Chris Klug Foundation's mission to promote organ, eye, and tissue donation awareness and help people waiting for life-saving transplants, with the partnership having raised over $250,000 for CKF's programs since 2012.