, a mountain range on the border between Uganda and the Democratic Republic of the Congo. Lying just north of the Equator, it extends for about 75 miles (120 km) between Lakes Albert and Edward and is flanked by arms of the Great Rift Valley. Margherita Peak, the 16,763-foot (5,109-m) summit of Mount Stanley, is the highest point in the range and the third highest peak in Africa. The range was first visited by a European explorer, Henry M. Stanley, in 1889, during his last voyage to Africa. It may be the “Mountains of the Moon” mentioned by Ptolemy and thought by ancient scholars to be the source of the Nile River.