A bullet train runs on Renjiashan Bridge of Xi'an-Chengdu high-speed railway during a simulated run in northwest China's Shaanxi Province, Nov. 22, 2017. The Xi'an-Chengdu line is China's first rail route to run through the Qinling Mountains, which are the natural boundary between north and south China. It will begin operation on Dec. 6. [Photo/Xinhua]