Clouds over the Sand Dunes
Sand Dunes National Monument in Colorado. My wife and I spent three days here on a recent trip that went from Ft. Collins, Colorado to Hidden Lake, New Mexico then to Taos, and continued back into Colorado for stops at the Sand Dunes, Silverton, Ouray, and Florissant.
These are the tallest dunes in North America rising approx. 750'. They are located at the base of the Sangre de Cristo mountain range near Alamosa, Colorado.