Aerial photo taken on Jan. 13, 2019 shows workers laying the tracks for the Beijing-Zhangjiakou high-speed railway line at Guanting Reservoir grand bridge in north China's Hebei Province. Track laying work of the Beijing-Zhangjiakou high-speed railway line at Guanting Reservoir grand bridge was completed on Sunday. The 174-km-long railway, connecting China's capital Beijing and Zhangjiakou of north China's Hebei Province, is a major transportation project for the 2022 Winter Olympic Games. (Xinhua/Yang Shiyao)