The range is about 120 km (75 mi) long and 65 km (40 mi) wide. It consists of six massifs separated by deep gorges: Mount Baker, Mount Emin, Mount Gessi, Mount Luigi di Savoia, Mount Speke, and Mount Stanley. Mount Stanley is the largest and has several subsidiary summits, with Mount Margherita being the highest point. The rock is metamorphic, and the mountains are believed to have been squeezed upwards by plate movement. They are in an extremely humid area, and frequently enveloped in mists. There are a number of small glaciers, with a total area of less than 4 sq km.
The first European sighting of the Ruwenzori was by the expedition of Henry Morton Stanley in 1889 (the aforementioned mists are considered to explain why two decades of previous explorers had not seen them). On June 7, the expedition's second-in-command and its military commander, William Stairs, climbed to 10,677 feet, the first non-African ever to scale the range's tallest peak. The first ascent to the summit was made by the Duke of Abruzzi in 1906.