The Richat Structure, also called Guelb er Richât (Arabic: قلب الريشات) is a prominent circular geological feature in the Sahara's Adrar Plateau, near Ouadane, west–central Mauritania, Northwest Africa. In the local dialect, rīšāt means feathers and it also is known locally in Arabic as tagense. Tagense refers to the circular opening of the leather pouch used to draw water from local wells. It is an eroded geological dome, in diameter, exposing sedimentary rock in layers that appear as concentr…