Once-secret installation now draws visitors worldwide

On a bright August afternoon, Boston Thomas stood at the mouth of a mountain, trying to wrap his head around what was hidden inside.

The 20-year-old from the United States had first read about the 816 Project on online travel agency Trip.com. The photos alone were enough to lure him halfway across the world. Now, in the remote hills of Baitao subdistrict in Chongqing's Fuling district, Thomas found himself confronted with a scale that defied comprehension.

From the outside, it appears as little more than nondescript concrete portals cut into the green slopes. Inside, however, lies an entirely different universe.

It is a labyrinth of caverns and tunnels hewed in total secrecy by more than 60,000 workers between 1966 and 1984. Originally designed to house a plutonium production facility, the project was scrapped before it ever went operational.

"I find myself particularly interested in this project," said Thomas, who studies emergency management and fire science at the University of Alaska Fairbanks.

He said that he would think in terms of contingency systems — how states organize to brace for catastrophes that hopefully never materialize. "It helps me better understand the differences between both the American system and the Chinese system, and how both can be bridged and how the aspects of either can play off one another."

Thomas walked in with his family, stepping out of the August heat and into the chill air of the cave.

Described by People's Daily as China's second nuclear material industrial base, it is the world's largest artificial cave. For decades, it was absent from official maps. Declassified in 2002 and opened to the public in 2010, the site has since beckoned visitors into its depths.

Visitor numbers have surged over the years. Last year, nearly 900,000 people explored its vast network of caverns and tunnels, a dramatic increase from fewer than 20,000 in 2014, according to Feng Jun, deputy general manager of the 816 Project Scenic Area.

Tourism magnet

The project was part of the Third Front Movement, a massive industrial campaign launched across 13 inland provinces and autonomous regions from 1964 to 1980.

With a total investment of 746 million yuan ($110.7 million), the 816 Project spanned 18 years — eight of blasting, excavation and concreting to carve out the cavern complex, followed by a decade of interior construction, equipment installation and plant fit-out — before the order to stand down came in 1984.

The facility never produced a gram of plutonium, and neither was any nuclear material ever stored within its walls.

The complex comprises 18 massive caverns and more than 130 passageways, including pilot tunnels, branch tunnels and shafts. Visitors can walk through the reactor bottom cavity, the colossal reactor hall, the diversion tunnels and the thermal circuit building.

Modern lighting bathes the rock in blues and whites, and the reactor hall — the largest cave at nearly 80 meters high and 25 meters wide — is like something out of a science fiction movie.

Since January 2024, a 60-minute immersive live-action show, Cave 816, has been staged regularly.

"It is impressive. So big, and all these levels," said Adriana Hart, a visitor from Los Angeles. "This is really something that you have to come and see with your own eyes to (appreciate) how spectacular this place is."

For Zheng Zhihong, general manager of the scenic site, the goal is to transform the 816 Project into a world-renowned industrial heritage destination. Local authorities have woven the site into a broader itinerary called the 503 Geocentric Loop Tour, linking it with the dramatic natural landscapes of Wuling Mountain Grand Canyon and the Baiheliang Underwater Museum, one of the world's oldest hydrographic survey sites.

To cap it off, visitors can enjoy a glass of red wine and a meal at the on-site military-themed restaurant, where the cavernous, concrete-walled interiors provide a fitting backdrop to this globally promoted tour.

Contact the writers at dengrui@chinadaily.com.cn