The Paw Paw Tunnel was finally completed around 1850 (before the Civil War), with over 3 million bricks being used to finish the 3,188 foot long canal under the present day Maryland mountain, just over the Potomac River from the very small town of Paw Paw West Virginia. To give you some perspective, almost three Empire State Buildings on their side could fit in the tunnel. The tunnel connected the Washington, DC to Cumberland, Maryland route along the C & O Canal and was used until 1924. At the time, it was considered one of the great marvels of engineering.
Although the picture looks as if you can walk to the other end in a few minutes, the reality is it takes about 15 minutes to walk at a normal pace along the trail built by the National Park Service. In the above picture I used a flash on camera to illuminate the bricks and the trail through the tunnel. There are no lights inside.
The northern end of the tunnel.