The Empty Quarter, otherwise known as Rub’ Al Khali, is the largest contiguous sand desert in the world. It is so-called because this huge stretch of unbroken sand has defeated kings, adventurers, and nomads for thousands of years. In a region defined by deserts, the Rub’ Al Khali has come to be known as among the most daunting and inhospitable. And it is on an unfathomable scale.