The Qinghai-Tibet Plateau is called the "roof of the world", first of all because of its height. Compared with Europe, the Qinghai-Tibet Plateau is astonishingly high. In addition, the Qinghai-Tibet Plateau is also very large, including not only the entire Tibet Autonomous Region and Qinghai Province, but also parts of Gansu, Sichuan and Xinjiang provinces. Such a large area of ????high mountains is well deserved to be called the "Roof of the World".