The star attrac­tion of Namib­i­a’s Namib-Nauk­luft Nation­al Park is this clay­pan sur­round­ed by soar­ing, ever-chang­ing red-orange dunes that stop the flow of the Tsauchab Riv­er. In the native lan­guage, Sos­susvlei means “dead-end marsh.” The dunes that cir­cum­nav­i­gate the pale flat, dot­ted with leaf­less veg­e­ta­tion, are some of the lofti­est and old­est in the world. Many are well over 650 feet tall and thought to be 5 mil­lion years old. While the dunes vary in col­or, the ones dis­play­ing the bright­est shades of red—indicating a high con­cen­tra­tion of iron—are the old­est.