Geography of Tibet consists of the high mountains, lakes and rivers lying between Central, East and South Asia. Traditionally, Western (European and American) sources have regarded Tibet as being in Central Asia, though today's maps show a trend toward considering all of modern China, including Tibet, to be part of East Asia. Tibet is often called "the roof of the world," comprising tablelands averaging over 4,950 metres above the sea with peaks at 6,000 to 7,500 m, including Mount Everest, on the border with Nepal. It is bounded on the north and east by the Central China Plain, on the west by the Kashmir Region of India and on the south by Nepal, India and Bhutan. Most of Tibet sits atop a geological structure known as the Tibetan Plateau, which includes the Himalaya and many of the highest mountain peaks in the world.
Physically, Tibet may be divided into two parts, the "lake region" in the west and north-west, and the "river region", which spreads out on three sides of the former on the east, south, and west. The region names are useful in contrasting their hydrological structures, and also in contrasting their different cultural uses which is nomadic in the "lake region" and agricultural in the "river region". Despite its large size and mountainous nature, variation of climate across the Tibetan Plateau is more steady than abrupt. The "river region" has a subtropical highland climate with moderate summer rainfall averaging around 500 millimetres (20 in) per year, and daytime temperatures ranging from around 7 °C (45 °F) in winter to 24 °C (75 °F) in summer - though nights are as much as 15 °C (27 °F) cooler. Rainfall decreases steadily to the west, reaching only 110 millimetres (4.3 in) at Leh on the edge of this region, whilst temperatures in winter become steadily colder. On the south the "river region" is bounded by the Himalayas, on the north by a broad mountain system. The system at no point narrows to a single range; generally there are three or four across its breadth. As a whole the system forms the watershed between rivers flowing to the Indian Ocean – the Indus, Brahmaputra and Salween and its tributaries – and the streams flowing into the undrained salt lakes to the north.
East Tibet: The tortuous ways of Nu, Lancang and Jinsha Rivers cut through the majestic Hengduan Mountain range, creating breathtaking landscapes of high mountains and deep canyons. Higher in the north and lower in the south, the mountain and canyon area in the eastern part of Tibet presents a wide diversity of fauna and flora as well as a unique combination of snow-capped peaks and verdant hillside forests.
South Tibet: Mt. Everest soars to a height of some 8,848m skyward and together with several other mountain ranges with an average altitude of 6,000m, constitutes the Himalayan mountain range as the highest mountainous area in the south of Tibet. With the higher western end of this area being dry and freezing, the eastern region is temperate, humid and densely forested. Meanwhile, between the Himalayas and the Gangdise, the Yarlung Tsangpo River winds its way through this region leaving a fertile agricultural area of lakes, basins and river valleys along its course.
North Tibet: Vast plateaus in the north of Tibet, specifically around the Kunlun Mountain, the Tanggula Mountain and between the Gangdise and the Nyainqentanglha Mountains, cover 2/3 of the total area of Tibet. Dotted with numerous lakes and basins, the plateaus, among which Changtang Plateau is the best known, provide rich animal husbandry products for other parts of Tibet.