Eye of the Sahara, Mauritania

The Richat Structure, also known as the Eye of the Sahara, is a prominent geological circular feature in the Sahara desert in Mauritaniae. Visible from space, it has a diameter of almost 30 miles, and has become a landmark for shuttle crews. Initially interpreted as a meteorite impact structure, it is now argued to be a highly symmetrical and deeply eroded geologic dome that collapsed.