<P> The Richat Structure, also known as the Eye of the Sahara and Guelb er Richat, is a prominent circular feature in the Sahara near Ouadane, west--central Mauritania . </P> <P> The Richat Structure is a deeply eroded, slightly elliptical dome with a diameter of 40 kilometres (25 mi). The sedimentary rock exposed in this dome ranges in age from Late Proterozoic within the center of the dome to Ordovician sandstone around its edges . The sedimentary rocks comprising this structure dip outward at 10--20 ° . Differential erosion of resistant layers of quartzite has created high - relief circular cuestas . Its center consists of a siliceous breccia covering an area that is at least 30 kilometres (19 mi) in diameter . </P>

Where is the eye of the sahara located