The Sahara, known to Arabs as the Great Desert, is the worlds largest desert covering as it does an area as large as Europe. It covers most of northern Africa stretching from the Red Sea almost to the Atlantic seaboard, and from the Mediterranean Sea and Atlas Mountains deep into the savannah of the Niger River valley in central Africa.
The sand storms caused by strong north easterly winds, and a erratic rainfall of between a half inch and 4 inch per year, makes the Sahara one of the harshest places on Earth. Its surface features vary from rocky mountains, arid scrubland, drifting sands and high dune formations, to large salt flats formed by evaporating lakes lying 70 feet below sea level. The desert covers large areas of eleven countries: Morocco; Algeria; Tunisia; Libya; and Egypt to the north along the Mediterranean coast, and Western Sahara; Mauritania; Mali; Niger; Chad and Sudan to the south.
Following the last ice age the Sahara was a much more hospitable place, with more rainfall and lots more vegetation. It is known to have been populated since that time, and prehistoric man has left his mark with many thousands of petroglyphs of animals which lived in the region at that time. A petroglyph is a rock carving in comparison with rock art paintings, and they depict scenes of human and animal life. Fossils of dinosaurs predating these have also been found in the desert.
The population of the Sahara region descends from largely black African with the introduction of Arab blood, having spread down from the northern coastline. The most famous of the Berber tribes (to me anyway) being the Nubians of southern Egypt, the Moors of western and southern Sahara, and the nomadic Tuareg in their famous blue robes, romantically fighting off the might of the colonising French Foreign Legion. Although sparsely populated there are a few important cities which have grown up within the desert, again the ones I know best are Ghat in Libya, El Oued in Algeria, and Timbuktu now in Mali.
For over five millennium the only places where vegetation has been abundant is in the Nile Valley, and at the various oases scattered across its barren surface. Apart from the Nile there are few rivers that flow throughout the year, most of them being dry wadis except during the short annual rainy spell. There is however water flowing underground which in places breaks the surface naturally to form an oasis, or can be reached by sinking well shafts into the sand.
Tunisia and the Sahara have provided the backdrop for many motion pictures, much of the Star Wars location shots being done there, and a film set is still in situ in the desert.