Northwest of the Tibetan Plateau, between the northern slope of Kunlun and southern slope of Tian Shan, is the vast Tarim Basin of Xinjiang, which contains the Taklamakan Desert. The Tarim Basin, the largest in China, measures from east to west and from north to south at its widest parts. Average elevation in the basin is 1,000 m. To the east, the basin descends into the Hami-Turpan Depression of eastern Xinjiang, where the dried lake bed of Lake Ayding, at 154m below sea level, is the lowest surface point in China and the third-lowest in the world. With temperatures that have reached 49.6 C., the lake bed ranks as one of the hottest places in China. North of Tian Shan is Xinjiang's second great basin, the Junggar, which contains the Gurbantünggüt Desert. The Junggar Basin is enclosed to the north by the Altay Mountains, which separate Xinjiang from Russia and Mongolia.