Japanese tunnel (lookout?) above Chai Wan

I'd seen this on an earlier hike, but went back on Sunday for another look. It was disappointing in that there was nothing much in the way of a tunnel. Still, it's an unusual layout, in that there is a deep (1.5-2m) square hole, with a short 2m tunnel leading into the hill beside it.

One possibility is that work on the tunnel had only just started, explaining the short tunnel. I think a more likely explanation is that it was some type of lookout post, given it's good view out to the eastern entrance to the harbour. Then the short tunnel would just have been for shelter.

Any other ideas?

Photos that show this place

Year: 2010

Year: 2010

Year: 2010