I take it this is a canal tunnel? It's amazing how the lack of surface movement, or reflected lights makes it look like a dry, circular tunnel. Only the matching stains on the brickwork give it away.
A very impressive image!
Yes it's quite a late canal tunnel, wide enough for boats to go in both directions, a tow path on both sides, it was originally gas lit. I was a little way into the tunnel, closer to the entrance would have caused exposure issues.
The tunnel's 9,081 feet (2,768 m) long hence the little dot at the far end, it's crossed by another canal at a higher level at the north portal.
I focussed the camera closer to the entrance then went further inside.