Aerial photo taken on May 15, 2019 shows the Polonggou grand bridge in Bomi County, Nyingchi of southwest China's Tibet Autonomous Region. Along the Sichuan-Tibet Highway, there are various new and old bridges. Crossing mountains and rivers, these bridges are not only the key junctions on this line, but also splendid landscapes. Over the past 60 years, the highway and the bridges along it have been continuously upgraded and perfected, which has become a miniature of the highway traffic development in China. (Xinhua/Li Xin)