This prominent circular feature in the Sahara desert of Mauritania is known as the Eye of Africa, The Richat Structure, and The Earth's Bulls-eye. It is often noted by astronauts because it forms a conspicuous 50-kilometer-wide (30-mile-wide) bull’s-eye on the otherwise rather featureless expanse of the desert which makes it clearly visible from space.
According to NASA, The Eye of Africa was once thought to be an asteroid impact crater, the structure’s flat middle and lack of shock-altered rock indicates otherwise. The possibility that the structure was formed by a volcanic eruption also seems improbable because of the lack of a dome of igneous or volcanic rock. Rather, the layered sedimentary rock is now thought by many to have been caused by uplifted rock sculpted by erosion. Why the Eye of Africa is nearly circular remains a mystery.
