Mountain Biking, Haleakala National Park
Concierge.com's insider take:
Imagine riding 30 miles from the 10,000-foot summit of a dormant volcano. Steeply downhill. On a bike. Sounds awesome—and it is—but this excursion isn't for everyone. To catch the sunrise at the top of Haleakala, you need to leave your resort as early as 2 am. Temperatures at the top dip below freezing, and it very well might rain on the way down, so riders must wear a helmet with a face shield and full rain gear—typically, a bright yellow slicker and pants. It's not much of a workout (except for the hand you use to squeeze the brake), but you share a road with vehicles, so there are some risks. Maui Downhill takes safety seriously and has an excellent track record (808-871-2155; www.mauidownhill.com). Afterwards, even the heavily bandaged say it's one of the best things they've ever done: Magnificent 360-degree views of Maui and beyond, a crash course in volcanic geology, and the opportunity to pass through multiple climatic zones, all before breakfast.