A 'reg' is a large, flat plain with stones and dust. The largest one is the Tanezrouft in southern Algeria. The Tanezrouft is one of the harshest places in the world. It's some hundreds of miles wide and long, no water, no vegetation, no people. The reg on the picture is in the neighbourhood of Tamanrasset, east of the Tanezrouft.
Back to Targui.