The Arabian Peninsula’s Empty Quarter, known as Rub’ al Khali, is the world’s largest sand sea, holding about half as much sand as the Sahara Desert. The Empty Quarter covers 583,000 square kilometers (225,000 square miles), and stretches over parts of Saudi Arabia, Yemen, Oman, and the United Arab Emirates. The Enhanced Thematic Mapper on NASA’s Landsat 7 satellite captured this image of the Empty Quarter on August 26, 2001.