Picture the Sahara, and an inhospitable landscape of ... that shed new light on the power held by priestesses in the ancient city.

From his roof, Sidi Mohamed Lemine Sidiya scans the mediaeval town of Oualata, a treasure that is disappearing under the sands of the Mauritanian desert ... quartet of ancient, fortified towns ...

An international team has sequenced the first ancient genomes from the so-called Green Sahara, a period when the largest desert in the world temporarily turned into a humid savanna-like environment.