The Richat Structure, also known as the Eye of the Sahara or blue eye of Africa, is a peculiar geological formation in the Sahara desert in Mauritania near Ouadane. Due to its size, the Eye is visible from space and it is a landmark for astronauts, helping them to realize thei position over the vast 3,600,000-square-mile desert.

The geological circular feature is nearly 50 kilometers wide and was initially thought to be the result of a meteroid impact, mainly due to its circular shape. Later on, its creation was attributed to a volcanic erruption, an argument which was never verified due to the absence of igneous or volcanic rock inside the dome. It is nowadays argued that it is the result of gradual erosion of an uplifted rock. However, the fact that the "rings", are equidistant to the centre and that the structure is nearly circular remains a mystery.