Photo taken on Dec 17, 2017 shows the construction site of Zhengpantai tunnel of an extension line of the Beijing-Zhangjiakou high-speed railway in North China’s Hebei province. The 52-km extension of the Beijing-Zhangjiakou railway to Hebei’s Chongli district, where most of the 2022 Olympic skiing events will be held, is expected to be completed by the end of 2019.[Photo/Xinhua]

Photo taken on Dec 17, 2017 shows the construction site of Zhengpantai tunnel of an extension line of the Beijing-Zhangjiakou high-speed railway in North China’s Hebei province. The 52-km extension of the Beijing-Zhangjiakou railway to Hebei’s Chongli district, where most of the 2022 Olympic skiing events will be held, is expected to be completed by the end of 2019. [Photo/Xinhua]