Eureka Dunes, Death Valley National Park
The Eureka Valley is a pain to get into, with a bone-jarring ride over at least 10 miles of washboard road, and a lot more if you come in from the south. The initial attractions are the big dunes, perhaps the tallest in North America, rising 600 feet above the desert floor. But look southeast from the tallest, and you'll see fantastic serpentine shapes of a series of dunes that are perhaps one-third as high but far more picturesque. It's a trek down to them but worth it. Carry some water.