Geograph - photograph every grid square

Known to locals as the Blue Pool or the Blue Water, this 6.1 metre (20 feet) internal diameter brick lined vertical shaft is 4 metres deep. Although the pool now looks black in colour and heavy with algal growth, it used to be the most amazing blue colour with water so clear you could see the bottom — it was like looking through a blue diamond.
I recently discovered that many local youths used it as a swimming pool.
I have been trying to discover the original purpose of this redundant feature but nobody (so far) knows. Most locals have never heard of it so I have started the ball rolling by putting up a web page to act as a nucleus for the Torwood Blue Pool Investigation where you can contribute your knowledge or just keep up to date with progress: Link