Mystery of the desert: The lost cities of the Nigerien Sahara

A long trek across the desert of northeastern Niger brings the visitor to one of the most astonishing and rewarding sights in the Sahel: fortified villages of salt and clay perched on rocks with the Saharan sands laying siege below.

Generations of travellers have stood before the “ksars” of Djado, wondering at their crenelated walls, watchtowers, secretive passages and wells, all of them testifying to a skilled but unknown hand.

Who…