Geography
A bullseye pattern in the Sahara is so vast it's easiest to see from orbit
The Richat Structure in Mauritania is a roughly 40-kilometre-wide set of concentric rock rings, so large it was first mistaken for a possible impact crater; geologists now attribute it to a dome of rock pushed up and then eroded flat over millions of years. Astronauts have used it as a naked-eye landmark since the Gemini missions of the 1960s.