Ad-Dahna Desert passages which can be several kilometers long. Local Bedouin have always known these caves and some were used as water supplies. They were first systematically studied in the 1981, and later explored and reported by the Saudi Geological Survey. Ad-Dahna Desert The ad-Dahna Desert is the central division of the Arabian Desert. It is a corridor of sandy terrain forming a bow-like shape that connects an-Nafud desert in the north to Rub' al-Khali desert in the south. Its length is more than 1,000 km siding Twaik Mountains from the east and does not exceed 80 km in width. It is
Geography of Saudi Arabia Sea escarpment does from the west. In the north, the An Nafud—sometimes called the Great Nafud because An Nafud is the term for desert—covers about 55,000 square kilometers at an elevation of about 1,000 meters. Longitudinal dunes—scores of kilometers in length and as much as ninety meters high, and separated by valleys as much as sixteen kilometers wide—characterize the An Nafud. Iron oxide gives the sand a red tint, particularly when the sun is low. Within the area are several watering places, and winter rains bring up short-lived but succulent grasses that permit nomadic herding during the winter and spring.