Tassili n’Ajjer

Prehistoric art proving the Sahara was once green and full of water

Tassili n'Ajjer, the "plateau of rivers," spreads across more than 72,000 square kilometres of south-eastern Algeria toward the borders of Libya and Niger, between the oasis towns of Djanet and Illizi. It is sandstone country, stained near-black to dull red by desert varnish and eroded into rock forests, deep gorges and nearly 300 natural arches, a landscape UNESCO compares to the surface of the moon. Its highest point, Adrar Afao, reaches 2,158 metres.

The plateau also holds one of the most important collections of prehistoric rock art in the world. More than 15,000 paintings and engravings have been identified, and together they bear witness to climate change, animal migrations and human life on the edge of the Sahara. The art falls into five traditions. The oldest, the Archaic, goes back to around 10,000 BCE; then come the Round Head paintings of hunter-gatherers, featureless round-headed figures that seem to float on the rock; then the Bovidian or Pastoral period, when domesticated cattle and herders arrived; then horses, before 1000 BCE; and finally camels, the animals of the trans-Saharan caravan trade. Antelopes, crocodiles and water-dependent animals like the hippopotamus appear in country where they have been gone for thousands of years, along with people hunting and dancing.

Some of the green Sahara survives. The higher eastern half holds open woodland of the endangered Saharan cypress, one of the longest-lived trees on Earth, and a small population of West African crocodiles survived on the plateau into the 20th century.

Tassili was already well known by the early 20th century, but Westerners came to know it largely through sketches made by French legionnaires in the 1930s, especially Lieutenant Charles Brenans, and the archaeologist Henri Lhote led famous expeditions there from 1956. Lhote's work also did harm: his team was accused of faking images and of brightening the paintings for tracing and photography, which damaged their original colours beyond repair.

Tassili n'Ajjer has been a national park, a biosphere reserve and, since 1982, a UNESCO World Heritage Site. It is managed by the Tassili Park Office, and tourism is tightly controlled: visitor groups must always travel with an official guide.