A vast area of primary tropical forest dominated by two spectacular extinct volcanoes, Kahuzi and Biega, the park has a diverse and abundant fauna. One of the last groups of eastern lowland (graueri) gorillas (consisting of only some 250 individuals) lives at between 2,100 and 2,400 m above sea-level.
The park is situated in the eastern part of the country, 50 km west of the town of
Bukavu, near Lake Kivu and the Rwandan border. It consists of a smaller sector on the eastern side covering part of the , and a larger western sector in the Zairean central basin. The two zones are connected by a narrow corridor. The entrance to the park is at Tshivanga, on the eastern side. Mitumba Mountains
The 75,000 ha eastern sector is entirely montane. The massif is part of the
Mitumba Mountain range, the western mountains of the Great Rift Valley. The two main peaks, Mount Kahuzi (3,308 m) and (2,790 m) are extinct volcanoes, and the massif dates from the late Tertiary or early Quaternary. Mount Biéga
The lowland sector in the Zairean central basin covers the watersheds of the tributaries of the Luka and Lugulu rivers. These both drain into the River Lualaba. The extension lies below 1,500 m apart from isolated peaks such as
(1,700 m), and consists of mountains cut by deep valleys. Undulating terrain in the west forms a belt between the two zones. Mount Kamani
The western zone is forested by equatorial rainforest, with transition forest between 1,200 m and 1,500 m. In the eastern zone, six different primary vegetation types have been distinguished: mountain rainforest, high-altitude rainforest, swamp forest, bamboo forest, subalpine heather and swamp and peat bog.
The park was established to protect 200-300 eastern lowland (Grauer's) gorilla occurring mainly in the forests at 2,100-2,400 m, but also in the lower rainforest. The 'mosaic' of biotypes makes the park an excellent gorilla habitat. Other primates include eastern chimpanzee, and numerous Cercopithecinae and Colobinae. Other mammals include elephant, forest hog and many antelope and duiker. Avifauna includes the endemic Rockefeller's sunbird, Grauer's broadbill, Grauer's warbler and Shelley's crimsonwing.
Endemic mammal species include giant gennet, Aquatic civet, Maclaud's horseshoe bat,
Ruwenzori least otter shrew, owl-faced monkey, eastern needle-clawed galago, Thomas' tree squirrel and Alexander's bush squirrel.
Fifteen villages of shifting cultivators were located in the eastern sectors of the park when it was created and continue to be occupied. The park is situated in one of the most densely populated areas of the country. Some 90% of the population of Kivu is rural, mainly dependent on agriculture. Seven separate tribal groups live around the park including the Pygmy, Barega and Bashi peoples. Traditional livelihoods are based on shifting agriculture and subsistence hunting.