 As it is these places were virtually never visited by tourists, except by some trans-Saharan expeditions in less volatile times.Along with some on the ancient settlements listed below, other tourist highlights in the Mauritanian Sahara include the Richat Structure just beyond Ouadane, Fort Saganne, the nearby Amojjar Pass and the sandy Tifoujar Pass; Terjit oasis and the medieval ruins of Ksar el Barka.The old cities of Ouadane, Chinguetti, Oualata, Tichitt, Ksar el Barka, Aoudaghost and Koumbi Saleh are all vestiges of a rich past during the apogee of the trans-Saharan trade from Black Africa.