The River Hyndburn drops into a culvert that takes it around 300m under a field. The outfall is iconic for me as a draining classic with it's large brick arch projecting out the ground.
Inside the stream bed changes from lose rocks to the natural bedrock, a series of pools and cascades making the going interesting.
A large chamber towards the end marks a slight change in direction.
There's a couple of side pipes, the largest a brick tunnel that rises in a series of steps but is blocked off at the top. Possibly a drainage adit for a disused mine.