Darfur covers an area of 493,180 square kilometers (190,420 sq mi), approximately the size of mainland Spain. It is largely an arid plateau with the Marrah Mountains (Jebel Marra), a range of volcanic peaks rising up to 3,042 meters (9,980 ft) of topographic prominence, in the center of the region. The region's main towns are Al Fashir and Nyala.
There are four main features of its physical geography. The whole eastern half of Darfur is covered with plains and low hills of sandy soils, known as goz, and sandstone hills. In many places the goz is waterless and can only be inhabited where there are water reservoirs or deep boreholes. While dry, goz may also support rich pasture and arable land. To the north the goz is overtaken by the desert sands of the Sahara. A second feature are the wadis, which range from seasonal watercourses that flood only occasionally during the wet season to large wadis that flood for most of the rains and flow from western Darfur hundreds of kilometres west to Lake Chad. Many wadis have pans of alluvium with rich heavy soil that are also difficult to cultivate. Western Darfur is dominated by the third feature, basement rock, sometimes covered with a thin layer of sandy soil. Basement rock is too infertile to be farmed, but provides sporadic forest cover that can be grazed by animals. The fourth and final feature are the Marrah Mountains and
Daju Hills, volcanic plugs created by a massif, that rise up to a peak at Deriba crater where there is a small area of temperate climate, high rainfall and permanent springs of water.
Remote sensing has detected the imprint of a vast underground lake under Darfur. The potential water deposits are estimated at 49,500 km2 (19,110 sq mi). The lake, during epochs when the region was more humid, would have contained about 2,500 km3 (600 cubic miles) of water. It may have dried up thousands of years ago.