A 500ft high Travertine Curtain blocking the exit from Wadi Darbat. It should really be referred to as Tufa, a precipitate of water containing dissolved carbonate minerals. As the water evaporates it deposits the carbonates that form this spectacular cliff face. During the monsoon period, this can quite often be hidden behind a deluge of water.
The technical description from my geology book says:
Rillenkarren.- Are forms of dissolution on the surface of the rocks that consist of small channels separated by sharp crests configuring a network of tight more or less parallel gullies next to each other. Its Genesis is linked to the dissolution of the rock by the sheet of water that forms on it as a local run-off.