The Richat Structure, also called Guelb er Richât, the Eye of Africa, Eye of Mauritania or Eye of the Sahara is a prominent circular feature in the Sahara's Adrar Plateau, near Ouadane, west–central Mauritania, Northwest Africa. It is an eroded dome, 40 kilometres (25 mi) in diameter, exposing sedimentary rock in layers which appear as concentric rings. Igneous rock is exposed inside and there are spectacular rhyolites and gabbros which have undergone hydrothermal alteration, and a central megabreccia. The structure is also the location of exceptional accumulations of Acheulean archaeological artifacts.
