What goes up must come down. And on the volcano Haleakala, that means cycling from summit to sea level. It can be challenging for novice riders; you're on the same road as the cars winding their way up to take in the view. Go self-guided if you're confident—or join an escorted tour. Once you've mastered the motion (and the 21 switchbacks along the road), effortless downhill freewheeling rewards you with unsurpassed views of almost every part of the island.