Chongqing - Hidden deep in a remote mountain of Fuling District, far away from the hustles and bustles of urban Chongqing, the 816 Nuclear Plant was once China's top-secret underground military project but has been turned into a scenic area in recent years, attracting tens of thousands of tourists to come and visit.

Located on the Jianzi Mountain of Fuling's Baitao Town, a place that disappeared from China's maps for decades, the 816 nuclear military plant is perfectly concealed in the range of mountains nearby. It feeds on the abundant water resources of the Wujiang River.

The 816 Project first started construction back in 1966 with a total investment of CNY740 million, a gigantic sum of money at a time when China's gross domestic product (GDP) barely reached CNY500 billion. More than 60,000 engineering soldiers of the People's Liberation Army are said to have participated in the construction of the military base, and 56 people even devoted their lives to the risky project.

The ambitious and highly confidential plan to build this military nuclear plant enhanced China's national defense capability. It prevented possible foreign invasion and nuclear attacks during the height of the China-Soviet Union tensions in the 1960s.

However, the project was temporarily postponed in 1981 and then again in 1982 and was officially terminated two years later. By the time when the 816 nuclear plant was turned into a chemical fertilizer factory some 30 years ago, it had already completed 85% of the construction work and 60% of the installation work. The underground nuclear reactor hall was then the world's largest artificial cave with 21 kilometers in length and 79.6 meters in height.

Hailed as "The Three Gorges in A Cave and The Great Wall Underground," the 816 nuclear plant boasts a total floor area of more than 100,000 square meters, over 130 branch tunnels, and some 600 numbered rooms. The artificial cave could withstand the force of 1 million tons of explosives as well as a magnitude eight earthquake. It represents China's most advanced engineering level in its science and technology industry back then.

On April 8, 2002, the then Science, Technology, and Industry Commission for National Defense of the People's Republic of China, a now-dissolved constituent of the State Council, approved the declassification of the existence of the State Council the 816 cave. And in April 2010, the relics of the 816 nuclear military plant project were officially opened to the public as a tourist spot, which is a rather unusual twist of fate for the living evidence of the Cold War history.

Entrance tickets to the 816 scenic village are currently sold at CNY80 per person, with the disabled, seniors above age 65, retired officers or active servicemen, family members or descendants of revolutionary martyrs, in-service medical workers, and children shorter than 120 centimeters free of charge.