The plateau of the Tassili n'Ajjer is located in the southeast, and its outstanding collection of prehistoric rock art saw it added to the UNESCO World Heritage List in 1982.

It is crossed by ergs (sand dunes), regs (stony terrain), as well as volcanic massifs in the far south.

However, it rarely snows and floods, sometimes reviving the wadis (river valleys) that have been dry since prehistoric times.

The subsoil is full of water in the Albian Aquifer which extends under a large part of the Algerian Desert, a remnant of the steppe climate that the region experienced 10,000 years ago.

Vast monotonous hamadas (hard rocky desert plateaus) like the Tademaït plateau between El Goléa and In Salah connect the large geographical areas of the Sahara.