Tassili n’Ajjer is a national park in the Sahara desert, located on a vast plateau in southeastern Algeria, bordering Libya, Niger, and Mali. It covers an area of roughly 80,000 sq. km. and contains one of the most important collections of prehistoric rock art in the world; it was inducted into the UNESCO World Heritage Site list in 1982. In 1986, UNESCO declared the area a Biosphere Reserve.
The plateau is composed largely of sandstone, and the natural erosion has resulted in hundreds of natural rock arches and other spectacular land formations — the ‘forests of stone’. Because of the altitude and the water-holding properties of the sandstone, the vegetation is somewhat richer than in the surrounding desert, and includes scattered woodland of the endangered endemic species of the Saharan cypress — one of the oldest trees in the world — and the Saharan myrtle. The literal English translation of Tassili n’Ajjer is ‘plateau of rivers’. Relict populations of the West African crocodile persisted in the Tassili n’Ajjer until the twentieth century. Various other fauna still reside on the plateau, including Barbary sheep, the only surviving type of the larger mammals depicted in the rock art of the area.