Japanese tunnel at Lion Rock [????- ]

I've never been up to the top of Lion Rock before, so yesterday we put that right. The air has been very clear these last few days so there were great views. Then as we walked down from the eastern peak (the lion's tail) I noticed this to the left of the path.

The marker position is approximate, but it's only a short distance down from the peak. I stuck my phone in to take a photo but didn't go inside.

It looked like a typical short tunnel to a dead-end, but looking at the photo I wonder if there is a turn to the left at the end. Something to check on another day.