The ensemble of paintings and rock engravings preserved on this high plateau, which is situated to the south-east of the Algerian Sahara and bordered by Libya, Niger and Mali, is among the most important of the prehistoric period. The zone covers an area of 72,000 km2 and is situated at a median altitude of 1,500 m. It is a triangular sector defined to the north-west by the abrupt cliff which, from Amguid to the border of Niger, dominates the ergs of Admer and Tihodaine; to the north, by the trail from Tarat to Amguid; and to the east, by the borders of Niger and Libya.

The tribes of the Ajjer Tuareg still wander on the barren, arid plateau cut by canyons, exploiting the meager vegetal resources with their nomadic flocks. However, during the prehistoric period, Tassili benefited from climatic conditions which were more favorable to human occupation. The abundance of game, the possibilities of animal husbandry and of pastoral life which lay within immediate proximity of impregnable defensive sites constitutes the basic factors which favored population development.

From about the year 6000 BC to the first centuries of the Christian era, the various peoples who inhabited this area left numerous archaeological traces: settlements, tumuli and enclosures which have yielded abundant ceramic material. Nonetheless, it is the paintings and the multifold rock engravings, found on the walls protected by rocky projections, to which Tassili owes the world renown it gained after 1933, the date of their discovery. To the present time, fifteen thousand of them have been inventoried and catalogued; specialists feel that the archaeological reserve could well be double this number. These paintings cover several periods each of which corresponds to a particular fauna, yet each may be equally as well characterized by stylistic differences without reference to an ecosystem:

• The naturalistic period (the oldest). The fauna represented is that of the Savannah.

• The period known as “archaic”. The extremely numerous fauna correspond to the humid climate. The system of graphic representation has changed: small schematic figures or colossal forms assume the aspect of pictograms charged with an evident magical finality;
• The Bovidian period (between 4,000 and 1,500 BC), dominant period in terms of the number of paintings. The representations of bovine herds, the scenes of daily life, which incorporate a renewed naturalistic aesthetic, are among the most well-known of prehistoric mural art.
• The Equidian period, which covers the end of the Neolithic and the Proto- historic periods, corresponds to the disappearance of numerous species from the effects of the dryness and to the appearance of the horse (representations of wild horses and of domesticated horses harnessed to wagons).

• Finally, the Cameline period, during the first centuries of the Christian era, coincides with the onset of the hyper-arid desert climate and with the appearance of the dromedary.

The most important group of paintings is situated to the east of Djanet in the National Park administrated by the OPNT (Office du Parc National du Tassili). Other remarkable works of rock art are found, to the north, in the region of the Wadi Djerat, near Illizi; and, also, the sites of the plateaus of Tadjilahine, Tasghirt, Dider, Ighassan and Adrar should be mentioned.

While primarily under consideration as a cultural site, Tassili d’Ajjer is also worthy of consideration on natural criteria. Tassili d’Ajjer meets natural criteria, being an outstanding example of man’s interaction with his environment and containing superlative natural phenomena of exceptional natura beauty. The geological formations are of outstanding scenic interest, with Precambrian crystalline formation and eroded sandstones forming “forests of rock”. The flora and fauna shows relationships to prehistoric periods when the Tassili region was considerably more moist; that humans knew such conditions is revealed by the many rock engravings and paintings which show species dependent on water (such as hippopotamus), as well as species which have been extinct from the region for at least several thousand years (buffalo, elephant, rhino, giraffe); more recent paintings show cattle herders, which may have helped bring about the drier conditions in this part of the Sahara.

The ancient artworks are of outstanding interest in demonstrating a long-extinct relationship between man and his environment.

Tassili appear to be a unique area in terms of the combination of geological features and cultural elements which reveal the wetter periods of southern Algeria.