Farther north the western depression, sometimes known as the Central African trough or Albertine rift-valley, is occupied for more than half its length by water, forming the four lakes of Tanganyika, Kivu, Albert Edward and Albert, the first-named over 400 m.
Other volcanic peaks rise from the floor of the valleys, some of the Kirunga (Mfumbiro) group, north of Lake Kivu, being still partially active.
The Kagera, the largest and most important of the lake affluents, which has its rise in the hill country east of Lake Kivu, and enters the west side of the nyanza just north of 1° S., is described in the article Nile, of which it is the most remote head-stream.
Mitumba range extends from the south-eastern frontier of the colony, in a north-easterly direction towards Lake Tanganyika, and northwards along the western shore of that lake past lakes Kivu and Albert Edward to Albert Nyanza, forming the western edge of the western or Albertine rift-valley.
It includes some of the volcanic peaks which, north of Lake Kivu, stretch across the rift-valley and attain heights of 13,000 and 14,000 ft.; Albert Edward Nyanza and part of the Semliki river; part of Ruwenzori, the so-called" Mountains of the Moon,"with snow-clad heights exceeeding 16,50o ft.