Ouadane

Ouadane is one of Mauritania's four ancient caravan towns (along with Chinguetti, Tichitt and Oualata), founded in the 12th century on a rocky promontory, with the stone ruins of the old town slowly crumbling down the hillside while modern life continues in the new village next door. It's the closest base for reaching the Richat Structure ('the Eye of the Sahara'), a 40 km-wide circular formation visible from space, whose geological origin still isn't fully settled.