Perhaps the best heart-pounding adventures combine two thrilling activities -- case in point, heli-skiing, where you ride in a helicopter over rugged terrain to the top of a mountain, then jump out and ski down. It's especially popular in Alaska, where remote, pristine slopes draw backcountry enthusiasts from all over the world. A number of tour companies, including Valdez Heli-Ski Guides and Points North Heli-Adventures, operate in the state's Chugach Mountains. With a few thousand square miles of terrain and more than 1,000 inches (2,540 centimeters) of snow per year in some areas, this range is known for its ideal skiing conditions. And the runs are long, too; some can descend nearly 6,200 vertical feet (1,890 meters)!