The Eye of the Sahara, or Guelb er Richat, is one of the most astonishing geological formations on the planet: a gigantic ring of rock some 40 km across, with perfect concentric circles, rising out of the middle of the Mauritanian desert. It is so large that it can only be seen whole from space, which is why astronauts have used it for decades as a visual landmark over the monotonous vastness of the Sahara.
For a long time it was thought to be a meteorite crater; today geologists know it is actually an eroded dome: an upward bulge of rock layers caused by processes inside the Earth which, after millions of years of erosion, exposed concentric rings of rocks of different ages and colours. That mix of science, mystery and lunar landscape — which has even fed fanciful theories about Atlantis — makes the Eye of the Sahara a one-of-a-kind destination.
This guide covers the Guelb er Richat with a practical eye: what it is and how it formed, what you actually see on the ground, how to arrange the 4x4 excursion from Ouadane, what camping inside the structure is like, and what precautions to take in this remote part of the Sahara. It is an adventure for well-prepared travellers, but the reward — standing inside a geological wonder visible from space — is one you won't forget.
The Guelb er Richat is an eroded geological dome some 40 km across, formed over millions of years by the uplift and subsequent erosion of layers of sedimentary and igneous rock; its oldest rocks date back hundreds of millions of years (with Cretaceous layers, around 100 million years old, among others). It was once believed to be an impact crater, but today it is understood as a structure of internal origin. The International Union of Geological Sciences (IUGS) has listed it among the world's 100 most valuable geological heritage sites. The full geological and human history is told on our history page.
Read the full history ↓The Adrar plateau is the soul of Mauritania: this is where the Almoravids were born, at Azougui, and where you find the holy cities of Chinguetti and Ouadane with their manuscripts, the oases and the enigmatic Eye of the Sahara.
Read the history of The Adrar, heart of the desert →No exact prices: a scale from $ (budget) to $$$$$ (luxury), with 2-3 options per category.
Origins, formation and what the sources say.
The Guelb er Richat —'the Richat' to geologists, the 'Eye of the Sahara' or 'Eye of Africa' to everyone else— is a circular geological structure about 40 kilometres across on the Adrar plateau in northern Mauritania, near the town of Ouadane. It is made up of a series of concentric rock rings that, seen from above, form a giant eye or a bullseye in the middle of the desert. It is so large that you can only take it all in from the air or from space: at ground level you see curved ridges and valleys, but not the whole circle.
Precisely because of its size and its unmistakable shape, the Eye of the Sahara became famous as a visual landmark for astronauts. Since the earliest space missions, crews in orbit have used it as one of the few sharp features in the vast, monotonous expanse of the Sahara, which from above looks like an almost featureless sea of sand. That 'seen from space' fame is a key part of its legend.
On the ground, the Guelb is a lunar landscape of many-coloured rock: rings of sandstone, limestone and other sedimentary stone, with igneous rocks and an unusual 'megabreccia' at the centre. Each rock type has a different age and origin, which makes the structure a natural laboratory that geologists from all over the world have been studying for decades.
For a long time, the most widespread explanation for the origin of the Eye of the Sahara was that it was the crater left by a huge meteorite impact. The near-circular shape and the concentric rings seemed to fit that idea. Detailed geological studies, however, ruled out that hypothesis: none of the typical evidence of an impact (such as certain minerals and shock structures) has been found, and the local geology points to a different process.
Today the accepted explanation is that the Guelb er Richat is an eroded geological dome. Put simply: many millions of years ago, an intrusion of molten rock (magma) rose from deep inside the Earth without erupting, and pushed up the layers of sedimentary rock above it, like a finger pushing up a pile of blankets from underneath. Over time, erosion —wind, and water during wetter periods— wore that bulge down, eating away the layers of different hardness unevenly and exposing the concentric rings we see today, with the oldest rocks laid bare at the centre.
The rocks of the Guelb span an enormous stretch of time: some sedimentary layers date back hundreds of millions of years, with Cretaceous elements (around 100 million years ago) as well as much older rocks. At the core, rhyolites and gabbros (igneous rocks) altered by hydrothermal activity crop out, along with a central megabreccia. Together they tell the story of how the Earth bulged and eroded here over entire eras. It is pure geology, no meteorites required.
The Eye of the Sahara's strikingly perfect and unusual shape has fuelled all kinds of speculation. The best known links it to the mythical Atlantis, the island city that the Greek philosopher Plato described more than two thousand years ago as a city surrounded by concentric rings of land and water. Some mystery enthusiasts pointed to the resemblance between that description and the Guelb's rings, and even its approximate size, to argue that Mauritania was hiding the legendary Atlantis.
Geologists and archaeologists are categorical: there is no evidence at all that the Guelb er Richat was ever home to a city or a lost civilisation. It is a purely natural formation, the product of geological processes spanning millions of years, and there are no remains of buildings, canals or anything else that would suggest Atlantis. It is a fanciful hypothesis that circulates mostly in online videos and forums.
Even so, legends like this, together with the spectacular satellite images, helped make the Eye of the Sahara famous worldwide and sparked curiosity about Mauritania. The 'Atlantis' mystery, unfounded as it is, is now part of the site's appeal for visitors: many people come drawn by its enigmatic reputation and leave fascinated by something far more real and no less astonishing: the sheer scale of geological time written in the rock.
The scientific value of the Guelb er Richat gained formal recognition when the International Union of Geological Sciences (IUGS) included it in its list of the world's 100 most valuable geological heritage sites, a catalogue of key places for understanding the history of the Earth. There, the Eye of the Sahara stands out as an example of an eroded dome and of ring geology, studied and cited in research all over the planet.
In recent decades, the Guelb has also become one of the big draws of adventure tourism in Mauritania. Together with the caravan towns of the Adrar (Chinguetti and Ouadane) and oases such as Terjit, it is part of the desert circuits that run every winter, many of them via the seasonal charter flights to Atar. Ouadane, the nearest historic ksar, serves as the base for excursions to the structure.
The future of tourism at the Eye of the Sahara is closely tied to security in this remote part of the Sahara and to responsible care of the environment. It is a fragile site with no infrastructure, which means going with local operators, respecting the desert, and neither taking rocks away nor leaving rubbish behind. For the well-prepared traveller, though, the reward is huge: standing on the rings of a 40-kilometre geological wonder, under one of the clearest skies in the world, with millions of years of Earth's history beneath your feet.
