The White Sands National Monument lies in a valley between the San Andres mountains to the West, and the Jarilla Mountains to the Southeast, into which a number of rivers drain, and which has no outflow. The rivers drain areas rich in Calcium and Sulphates, and are actually dilute solutions of gypsum, into Lake Lucero, where the water evaporates, leaving the gypsum. The wind blows it into dunes which move across the countryside. The dunes are a blinding white, but their colour softens at sunset and makes them pretty photogenic.
White Sands, and the neighbouring town of Alamogordo are also (in)famous for being the site of the first Uranium bomb explosion in 1945.