Above the Arctic Circle lies Kobuk Valley National Park. The size of Delaware and lacking any roads or even official trails, this wilderness still feels uncharted. This national park is the home of the Great Kobuk Sand Dunes, where mountains of sand can stand almost 100 feet high and temperatures can soar to 100 degrees Fahrenheit. The annual migration of over half a million caribou has sustained human life in this forbidding climate since ancient times.