Another part of the Stroudwater Canal, bur unfortunately this section in front of the tunnel has not been restored yet.
The tow-path goes through this tunnel under the main railway line from Bristol to Gloucester whilst the canal is reduced to a 3 foot tube, just for water flow. The whole area needs to be opened up to it's original bridge form to allow boats to pass under the railway.
Best viewed with the magnify button above the pic.