The Queensury tunnel is 2501 yards long, completely straight and drops to the south. The strines cutting at the south end has been blocked off, resulting in flooding of the cutting to above the portal of the tunnel at its southern end. According to various reports, the tunnel is variably flooded to between 400 and 800 yards of its length. The tunnel is 430 feet below the hillside at its deepest point, presumably where it passes beneath Queensbury village, which directly overlies the tunnel.
Since abandonment, the tunnel was used by Leeds University for some physics experiments, although this does not appear to have happened recently.
There have been proposals to backfill the tunnel with landfill, however as yet this has not taken place. Inside the tunnel, there is evidence of survey work with areas highlighted with spray paint, including a 'fill line' just below the invert level of the roof. Also, reflective chainage markers have recently been placed in the tunnel, supplementing the older sprayed on numbers. Chainage is measured from the north end.
As the tunnel is blocked off at one end, there is no airflow through the tunnel. Consequently, the air inside the tunnel is very stale. This is immediately noticeable on entering. I got as far as chainage marker 86, (1900 yards) before the air became very poor, once I got a waft of sulphide gas (bad eggs) I decided that it was not a good idea to go further. This decline in air quality must be recent as there are reports where people have gone further.
Another website with some great pictures below