The Eye of the Sahara
The Richat Structure is a geological formation, called for its shape "the Eye of the Sahara".
It’s located in Mauritania, in the middle of the Sahara desert, near the town Ouadane, at an altitude between 400 and 450 m.
The structure is slightly elliptical, 50 km in diameter, dome. The concentric circles are composed of limestone and Paleozoic quartzite.
The difference in height between the rings is about 40 meters. The center is a giant conglomerate with a diameter of about 1.5 km.
The first assumption were to occur due to hit by meteorite impact but now geologists believe it is a product of uplift and erosion.
The cause of its circular shape is still unknown.