You'll be forgiven if you first read that as "The Eye of Sauron." Astronauts were the first to notice this 50-kilometer wide geological formation in Mauritania, in the middle of the Sahara Desert. Read about it and other wonders of nature in the post 13 Most Incredible Geological Wonders on Earth at Environmental Graffiti. Link
Sphincterish!
Abusive comment hidden.
(Show it anyway.)