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.