If you’ve ever used the train between Stroud and Kemble (typically the train to London) you will pass through Sapperton tunnel.
There’s actually two parts to the tunnel, the longer one being 1 mile, 104 yards long (1.7km) and a shorter one being 353 (323m) yards long. A short gap separates the two tunnels.
This gap is at the highest point on both sides.
Originally the tunnel was designed to be curved but for various reasons it ended up being a straight line. It was also shorter and less deep than the original planned one.
A footpath runs along the top of the tunnel through some woodland. Along the path are some large circular brick structures which are the tunnel air vents. For some reason these brick towers are different heights.
The shafts were probably used during the construction of the tunnel. Dig a number of deep shafts and from the bottom of the shaft dig horizontally in the directions the tunnel needs to go.
They’d also be used as extraction points for the soil and rock as the tunnel was being made. It’s a long way from the middle of the tunnel to the ends of it!
If you use the train you can spot the air shafts from the window. You need to be on the side where you can see the other line
