In this aerial photo taken on Jan. 11, 2018, a bullet train passing the Yelang River Bridge during the bridge's trial operation in Tongzi County, southwest China's Guizhou Province. The steel arch bridge spans as far as 370 meters over a karst valley. In southwest China's Guizhou Province, where endless karst hills dominate the land, modern transportation is made possible thanks to more than 20,000 bridges that cross over the valleys. The province easily justifies itself as a museum of bridges: among the world's 100 highest bridges, 46 are located in Guizhou. Over the four decades since China's reform and opening-up, generations of bridge builders have created various engineering miracles while battling technological challenges on tricky terrains. (Xinhua/Ou Dongqu)