The space opens out to reveal a large body of water – this was once a compensation lake for the nearby mill (which you passed as you walked up Tunnel Lane – this is now on private land, but you can see the buildings from the gate, as well as the sandstone folly). Lifford Lake was built in 1815 and is popular for fishing. I took a panoramic photo while I was there.
You can read more about Lifford here.
Pics taken by me, August 24th 2012. They are up on Flickr!