China has completed the Yiliang Tunnel, the longest tunnel ever built for a high-speed railway line designed to run at 350 kilometers per hour.
The tunnel cements China's position at the front of global rail engineering, adding a record-setting piece of infrastructure to what is already the world's largest high-speed network. Projects of this scale test the limits of tunneling and track design at top speeds, and finishing one signals how far the country's construction capabilities have come.
The milestone is part of a wider push to make the network faster and more far-reaching. On the Guiyang-Guangzhou high-speed railway, operating speeds are climbing to 300 kilometers per hour from 250, cutting travel times across a busy southern corridor.
China is also building its first sea-spanning high-speed railway capable of a 350-kilometer-per-hour top speed, a project that would carry fast trains across open water for the first time in the country's system.