Ruwenzori (rōˌwənzōˈrē) [key], mountain range, E central Africa, on the Uganda-Congo border, in the western arm of the Great Rift Valley between lakes Albert and Edward. This fault-block range is composed of ancient crystalline rock; Uganda's Kilembe copper mine is located in the range's eastern foothills. The snowcapped summits of the Ruwenzori include Mt. Margherita (16,798 ft/5,120 m) and Mt. Alexandra (16,750 ft/5,105 m). The peaks are invariably shrouded in mist, presenting an eerie aspect, and there are extensive glaciers and glacial lakes. The range may be the fabled "Mountains of the Moon," erroneously supposed by the ancients to be the source of the Nile.