In the south of the country is the Rub' al Khali, or "Empty Quarter", the largest contiguous sand desert in the world. It slopes from about 800 m (2,600 ft) near the Yemeni border, northwestwards nearly to the Persian Gulf. Another sandy desert, the Nefud, lies in the north central part of Saudi Arabia, and it is connected to the Rub' al Khali by a broad swathe of sand dunes and gravel plains known as Dahna.