Acacus Mountains

Listen for a moment. Out here the silence is so complete that you can hear sand moving. It slides off a dune crest with a faint hiss. The rock under your hand is warm, even in the shade, and it feels rough, like coarse paper. You are standing in the Acacus, also called the Tadrart Acacus, a range of dark sandstone in the far southwest of Libya. The town of Ghat lies to the west, and the Algerian border runs close by.

From a distance, the mountains do not look like mountains at all. They look like a ruined city. There are towers, walls, and narrow corridors, all carved by wind and ancient water. The stone is a deep rust brown, often coated in a black, glossy crust that geologists call desert varnish. Between the cliffs, rivers of orange sand fill the valleys. The colours shift through the day, from grey at dawn to copper in the late afternoon.

Here is the first surprise. This dry place was once green. Thousands of years ago, the Sahara went through long wet periods. Rain fell, lakes formed, and grasses covered land that is now bare sand. Elephants, giraffes, hippos, and herds of wild cattle moved through these valleys. People lived here too. And they left a record of what they saw, painted and carved on the walls of these rock shelters.

That record is the reason the Acacus is famous among archaeologists. The rock art here covers an enormous span of time, many thousands of years. In 1985, UNESCO listed the rock-art sites of the Tadrart Acacus as a World Heritage Site. The listing recognises the art as one of the most important records of how life in the Sahara changed, as the climate slowly turned from wet to dry.

The oldest images are mostly engravings. They are lines cut or hammered into the stone. Many show large wild animals, sometimes life-sized. Look closely and you may see the outline of an elephant, or the long neck of a giraffe. Scholars often call this the period of wild fauna. These carvings show animals that could not survive here today. That makes them a kind of climate diary, written in stone.

Later come the paintings. One style shows human figures with large, round, featureless heads. Researchers call them the Round Head figures. They float on the rock, sometimes in groups, sometimes alone. Nobody knows exactly what they meant. Some experts suggest they had a spiritual or ritual purpose. It is honest to say that their meaning is still debated, and that is part of their power.

Then the scenes change. Cattle appear, in large, carefully painted herds. People milk cows, gather in camps, and walk beside their animals. This is the pastoral period, when herding replaced hunting as a way of life. The paint was made from natural pigments, such as red and yellow ochre, a type of coloured earth. Some of these scenes are so detailed that you can see patterns on the cattle hides.

The final chapters show the desert drying. Horses and chariots appear first. Later, camels take their place, because camels can survive long journeys without water. By the time the camel arrives in the art, the Sahara looks much as it does now. In one long walk through these valleys, you can follow thousands of years of change — from hippos to camels.

Here is the second surprise, and it is a quiet one. Serious scientific study of the Acacus began in the mid twentieth century, led by the Italian archaeologist Fabrizio Mori. At a rock shelter called Wan Muhuggiag, his team found the remains of a young child. The body had been carefully preserved and wrapped, thousands of years ago. It is among the oldest known examples of deliberate mummification in Africa. That find suggests these desert people had their own complex beliefs about death.

The landscape itself carries its own wonders. The best known is the arch of Afzejare, a great span of sandstone that wind has hollowed into a natural bridge. Elsewhere, pillars rise alone from the sand like chess pieces. Wind does most of the work here now. It carries grains of sand that scrape the rock, year after year, very slowly opening holes and smoothing edges.

This is also Tuareg country. The Tuareg are a Berber people of the central Sahara, long known as traders and guides across the desert. Many local guides and drivers in this region are Tuareg, and they know the routes between the valleys and wells. If you share tea with them, it is usually poured from high above the glass, to raise a foam. The tea often comes in three rounds, each one tasting a little different.

The paintings are fragile, and they face real threats. Some have been damaged by graffiti, scraping, or by visitors who splash water on them to brighten the colours. That water slowly destroys the pigment. In 2016, UNESCO placed this site, along with Libya's other World Heritage Sites, on its list of heritage in danger. The best thing any visitor can do is simple: look closely, take photographs, and never touch the rock.

Before you move on, stand still once more. Notice how the shade of the overhang feels cooler on your skin. Look at the smooth floor of the shelter, worn by people who sat here long before written history. The same light falls on these walls as it did when the paint was fresh. As you walk back out into the sand, glance over your shoulder. The cliff will look empty from a distance... but now you know what it holds.