Signs of life in the Empty Quarter

An unlikely tree stands amid the seemingly endless dunes of the Rub' al Khali desert in the Arabian Peninsula. The Rub' al Khali, meaning Empty Quarter, is a vast sea of sand. Spreading across 250,000 square miles, it's the largest contiguous sand desert in the world, covering most of south-east Saudi Arabia, with smaller portions in Yemen, Oman and the United Arab Emirates. One of the driest places on Earth, almost nobody lives in Rub' al Khali, and much of the desert remains unexplored. Some of the dunes tower more than 800ft (244m) high, and the depressions in between, called sabkhas, can be so soft that vehicles, camels and people can easily become stuck.
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