Niger River in western Africa
In this photo, the Niger River flows through parched, landlocked Mali in Western Africa. "The Niger River flows north through an ancient sand sea before turning sharply east to skirt the edge of the dune-striped Sahara," according to the USGS. After the Nile and the Congo, the Niger is the third longest river in Africa. It is considered to be "the focal point" for the development of several key African civilizations. This photo was taken Feb. 8, 2003.