China just completed the excavation of the under-river section of the Chongtai Yangtze River Tunnel – a 14-kilometer-long high-speed rail tunnel 89 meters below the country's largest waterway, using the world's biggest tunneling machine.

Designed for trains traveling at 350 kilometers per hour, the tunnel was excavated by a domestically built titan called "Linghang," the world's largest – and likely smartest – shield-tunneling machine.

Excavating under the riverbed is like drilling through tofu – except the "drill" has a diameter of a five-story building (15.4 meters), and weighs 4,000 tonnes. Above the "tofu" is water pressing down with roughly 10 times atmospheric pressure.

But "Linghang" conquered the challenge of drilling over 11,000 meters of tunnel beneath the river with ease, thanks to its delicate hands and an intricate nervous system.

Equipped with over 500 sensors, the shield machine sends more than 80,000 threads of live data to its AI brain for every meter of excavation.

The process is "attended but unmanned," meaning humans no longer have to set each perimeter based on experience manually.

With the trickiest part now behind it, the Chongtai Yangtze River Tunnel is set to bring the Yangtze River Delta Economic Zone closer together.

This tunnel is a part of the Shanghai-Chongqing-Chengdu High-Speed Railway, connecting three major metropolitan areas, from China's coast to its hinterland.

Once operational, it will create a 2,000-kilometer economic corridor, linking over a quarter of China's advanced manufacturing industries and 40% of its key state labs.