Explore cinder cones and old lava flows from within Haleakala, possibly the largest dormant volcano on the planet. Formed by erosion rather than volcanic activity, the valley at the summit of Haleakala boasts much to marvel at and the packed cinder and soil underfoot makes for a relatively easy hike. Here you'll find the silversword, an endangered plant found nowhere else on Earth with an alien appearance that compounds the other-worldly appearance of this remote location. Ascending and looping up the mountain, the road to Haleakala National Park is equally spectacular, climbing through the clouds to the summit. Watch out for tour groups of cyclists on this road who freewheel down the mountain. These popular tours begin in the early hours of the morning so they can witness the sunrise over the island from the summit before they begin their two-wheeled kamikaze return back down the volcano.