The Richat Structure is a prominent circular geological formation in the Sahara Desert of Mauritania. It is also known as the Eye of the Sahara or Guelb er Richat. This structure is approximately 40 km in diameter and is composed of a nearly symmetrical circular array of sandstone and
From Wikipedia
The Richat Structure, or Guelb er Richât, often called the Eye of Africa is a prominent circular geological feature at the northwestern edge of the Taoudeni Basin, on the Adrar Plateau of the Sahara. It is located near Ouadane in the Adrar Region of Mauritania. In Hassaniya Arabic, rīšāt means feathers and it is also known locally in Arabic as tagense, referring to the circular opening of the leather pouch that is used to draw water from local wells.