A train enters a tunnel in the Hualongmen to Pengshan section of the southwest China's Chengdu-Kunming Railway, June 21, 2017. China will build its first undersea tunnel for high-speed trains, connecting two cities in eastern province of Zhejiang, according to local authorities. The train project, connecting the city of Ningbo with the island city of Zhoushan in east Zhejiang, is 70.92 km in total length, with an undersea tunnel section of 16.2 km, according to the construction plan. Trains are designed to run at 250 km per hour, cutting the trip between the two cities from 1.5 hours to less than 30 minutes. China's high-speed rail has reached 25,000 kilometers in length, accounting for more than 60 percent of the world's total. Zhejiang was among the earliest provinces in the country to build high-speed rail. (Xinhua/Kong Xiangwen)