China is a maritime nation with over 9,000 miles of coastline, dotted with ports. Compared to most other countries, it has a large number of naval bases. By dispersing its forces across many bases the Chinese Navy, formally known as the PLAN (People’s Liberation Army Navy), is protecting them against surprise attack. But some of it bases go further, offering underground tunnels to protect key warships and submarines.
China’s tend to be built directly into rocky outcrops which may provide many feet of overhead protection. The entrance is usually facing inland (but with water access) so that it is harder to hit from offshore.
The best known of these tunnels are two which protect the strategic submarine force. One built at Jianggezhuang Naval Base (36° 6’20.76″N, 120°35’2.39″E) near Qingdao provides a hiding place for ballistic missile submarines based there. And more recently one has been built at Yulin (18°12’8.97″N, 109°41’39.34″E). This is where a new base for nuclear submarines was constructed around 12 years ago. Yulin allows Chinese submarines (and aircraft carriers) easy access to the South China Sea, an important operating area.