Location: Ouadane, Mauritania. https://goo.gl/X8wddg
Initially interpreted as an asteroid impact structure because of its high degree of circularity, the Richat Structure is now regarded by geologists as a highly symmetrical and deeply eroded geologic dome.
Image 1: Landsat 8 Bands 6,5,4 in RGB
Image 2: World Imagery
Images Pan-sharped with hill shade derived from SRTM v3.