The MESQUITE FLAT SAND DUNES of Death Valley National Park (are they worth a visit???) 

Visiting the Mesquite Flat Sand Dunes in Death Valley National Park, California. Here, endless sand dunes between 10-100 feet in height were surrounded by rugged mountain ranges, all in the lowest region of the continent!!!
Definitely worth the 20 minute detour from the park office, just remember to bring a ton of water!!!