Usun Apau is a volcanic plateau covering an area of approximately 1,550 km2, and averaging 1000 meters in elevation. There are three extinct volcanoes in the center of the plateau – Selidang (1,370 m), Kenawang (1,280 m), and Mabun (1,280 m). The northern, eastern, and western edges of the plateau end in steep escarpments nearly 300 meters high. Three rivers drop from the northern edge of the escarpment, including the Julan River, which forms the Julan waterfall almost 245 meters high. Streams from the plateau form the headwaters of the
Rajang and
Baram rivers. ==Flora and fauna==