National Geographic : 1957 Feb
240 Shibam, City of Whitewashed Mud, Shimmers Like a Mirage in the Wadi Hadhramaut Suitable land is scarce. To make maximum use of a low mound between escarpment and river bed, Shibam thrusts walls 70 and 80 feet high. Lower walls, six feet thick, are windowless for defense. Elevators are lacking.