In the 1960s, in response to a complex international environment, China organized the construction of a series of large-scale underground military projects such as the top-secret "131" project, the 816 Underground Nuclear Project, and the 6501 Underground Project.
816 Underground Nuclear Project, for instance, hollowed out an entire mountain, constructed a massive artificial cavern out of reinforced concrete, the cave system totalling about 20 kilometers long and excavating approximately 1.51 million cubic meters of rock.
And this is just the information that has been revealed. In South Sichuan, Tibet, the Northwest, deep within mountain valleys and desert wilderness, there are even more undisclosed projects still under strict military administration.
Chen Yang surmised that this excavated mountain base was also a project of that kind.
