Tibet is locked by towering mountains. The Tibetan plateau is the highest in the world at an average height of 4,000 m. It has an area of more than 1.2 million sq km and a population of 18.5 million; 16.5 million are ethnic Tibetans and rest are Huis, Moinbas, Lhobas and Hans. In the north there is the Kunlun range and the Tanggula mountains, in the middle is the Gsngdise range and in the east the Hengduan range; in the south the Greater Himalayas.