The Rub' Al Khali desert in Saudi Arabia. Rub' Al Khali means the empty quarter. It is the 9th largest sand based desert in the world. The desert covers some 650,000 square kilometers (250,000 square miles) (the area between long. 44°30??56°30?E., and lat. 16°30??23°00?N), more than the combined land areas of the Netherlands, Belgium and France. It is one of the most inhospitable places on earth, and entirely uninhabitable.