Introduction to the Underground Military Readiness Cave: Under Chairman Mao Zedong’s call to dig deep holes and accumulate grain widely, and with the approval of the Central Military Commission, an underground military readiness cave was dug in ten years from 1958 to 1968. The underground combat readiness cave has a main passage of 3,100 meters and a Maoer Cave passage of 2,000 meters. It is a herringbone passage and is divided into three entrances: east, north and southwest. The north entrance is in Linshu, and the east and southwest entrances are in Jiangsu.