The pic from Radio Free Asia.
They are rapidly becoming "must read" Internet. It wasn't that way a few years ago ...
The caverns are capable of hiding up to 20 nuclear submarines based on reconnaissance satellites data collected. The harbor houses nuclear ballistic missile submarines and is large enough to accommodate aircraft carriers. The US Department of Defense has estimated that China will have five Type 094 nuclear submarines operational by 2010 with each capable of carrying 12 JL-2 intercontinental ballistic missiles. Two 950 metre piers and three smaller ones would be enough to accommodate two carrier strike groups or amphibious assault ships.
I had heard of the base (here on FR) but haven't paid much attention to it. Another link mentioned that the underground caverns can hold 20 subs when full.
Looks like a good military target for an underwater drone ...
Bkmk