File photo taken on July 1, 2006 shows the passenger train coded "Qing 1" passing the Tanggula Mountain Pass with an altitude of 5,072 meters above sea level, the highest of world's railway, in southwest China's Tibet Autonomous Region. The Qinghai-Tibet Railway turns 10 on July 1, 2016. The 1,956-kilometer-long railway, which began service in July 2006, is the world's highest and longest plateau railroad and also the first railway connecting the Tibet Autonomous Region with other parts of China. Ecological protection measures taken during and after the construction of the railway have ensured it was built as "a green railway". The alpine vegetation ecosystem has been effectively protected, the permafrost environment has been stable for years, the eco-function regions have been doing well and the plateau landscape remains intact. (Xinhua/Gaesang Dawa)