"Maui's most epic and unique hike is also one of its most challenging: Haleakalā Sliding Sands Trail drops into a vast crater, cuts across its floor, then goes up the other side before doubling back on a truly thrilling 11-mile out-and-back loop. The views are out of this world, with sweeping volcanic landscapes that might look more at home on the surface of the moon than on Maui. On a clear day, you'll be hiking above the clouds—and you can even spot the Mauna Loa and Mauna Kea volcanoes on the neighboring Big Island. Be prepared for an intense, all-day affair." - Todd Plummer