The Sahara is to a large extent a stone, gravel or rock desert. With only 20 %, sand deserts only represent a small part of the Sahara. The sand desert consists of a tableland of 200 to 500 m a.s.l. with extensive basins and valleys that are towered in the centre by the mountainous massifs of Hoggar and Tibesti. South of the massif there are hills and mountain lands. The highest point of the Sahara is Mount Emi Koussi in the Tibesti with 3,415 m a.s.l. The northeast part rises towards the south and reaches a height of nearly 2,000 m in the Djebel Uweinat. South of it lie the hills of the Ennedi. East of the Nile valley, in the Arabian and Nubian deserts, the country is bulged and then falls down abruptly to the Red Sea. There are also some large craters of meteorites in the Sahara. The largest is the Kebira crater with a diameter of 31 km.

In the usually drainless basins and valleys, there are many salt swamps and salt flats.. In Egypt, the Sahara is interrupted by the river oasis of the Nile. Together with the Niger, two permanent rivers flow through the desert; the Nile crosses the Sahara from South to North and the Niger flows in a large curve barely touching the desert.

The Sahara is the only desert on earth that has a large, coherent dry belt that is climatically classified as hyper arid. The Sahara belongs to the old world dry belt that begins in Mauritania and crosses North Africa and the Arabian deserts until it reaches China. If we include the deserts at the Horn of Africa, 76 % of the surface north of the equator is desert or half desert.