At fifty-five million years old, the Namib Desert, in western Namibia, is considered the oldest desert on Earth. In this image part of the Namib-Naukluft National Park is visible, which covers an area of almost 50,000 square kilometers (19,300 square miles). The park’s main attraction is Sossusvlei, a large white salt and clay pan in the center of the image. Sossusvlei is a basin for the Tsauchab River, an ephemeral river flowing from the east. The dunes in this area are some of the highest in the world. The tallest stands at around 325 meters (1,066 feet). The Namib Sand Sea is the only coastal desert in the world to contain large dune fields influenced by fog, the primary source of water.