Work on the plant began in 1966 as tension between China and Soviet Union. 816 plant, built to withstand up to 8.0-magnitude earthquakes, has 18 main caverns (the largest of which is 80 meters high) and 21 km of tunnels and passageways. The project was never finished after a 740 millions of RMB investment and the work stopped in 1984. The plant opened to domestic tourists in April 2010. Inside you can find a retro-futurist Chinese computer from the seventies.
In 1966, during the Sino-Soviet relation crisis, China started few national defence programs to prevent a possible Soviet invasion, such as Beijing Underground City and the 816 Nuclear Military Plant. After the approval of then-Premier Zhou Enlai, the base was built by more 60,000 engineering soldiers of the People Liberation Army. The surface of the cave is more than 104,000 mq. and the total lenght of the tunnels is more than 20 km. The project was cancelled in February 1984.
Related: Chinese nuclear tests during Sixties