Um, it's lovely. What is it?
It's called the Richat Structure, and it's located in the west African nation of Mauritania.
The photo was posted to Twitter last evening by Canadian astronaut Chris Hadfield, currently orbiting earth aboard the International Space Station (ISS).
Commander Hadfield has been delighting Twitter users since boarding the ISS on December 21, tweeting spectacular pictures of the Earth's surface as he passes overhead, and of daily life inside the space station.
"Tonight's finale: Undoubtedly one of the coolest space sights on Earth, the Richat Structure of Mauritania," he wrote last night.
Also known as the 'Eye of the Sahara', the Richat Structure is a 30-mile wide geographical oddity in the Sahara desert near the small oasis town of Ouadane.
Once thought to be an asteroid impact crater, scientists now believe it is a "symmetrical uplift (circular anticline) that has been laid bare by erosion".
So now you know.
