In this aerial photo taken on Sept. 25, 2018, workers building the Pingtang Bridge of the Pingtang-Luodian expressway in southwest China's Guizhou. The height of one of the bridge's towers measures 328 meters. Once completed, the Pingtang Birdge will be the highest concrete bridge in the world. 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/Yang Wenbin)