13. Richat Structure – Mauritania
Seemingly swirling and twisting and turning like a cyclone through the heart of the mighty Sahara Desert, the fantastic Richat Structure in the depths of Mauritania is something genuinely mysterious (although you will definitely have to take into the skies to see it!).
Scientists have puzzled for many years as to how the ideal circular set of concentric rings got there. Some believe it was an asteroid impact in centuries gone by. Others say it was the most simple procedure of natural geological attrition and erosion.
And then – of course – there are some people who believe it had been the production of extra-terrestrials, who passed this way and marked that a landing stage for future visits on the planet.