WALKERS at a beauty spot have been warned to be on their guard – after a mystery pothole appeared.
The hole was spotted near the Water Tower in Cleadon Hills and reported to Northumbrian Water.
Despite being only about a foot in diameter, its depth is unknown and there were concerns that because of its proximity to the Victorian waterworks it could be an opening to an underground well.
It has now been fenced off by the water company.
Cleadon ward councillor Jeffrey Milburn said: “I couldn’t believe the size of the hole.
“It might not be very wide, but it is deep. I threw a little pocket torch down it see if it would brighten it up, and it didn’t stop.
“I didn’t even hear it hit the bottom.
“I’ve got no idea how deep it is but people could easily be injured if they fell in.”
He contacted Northumbrian Water and South Tyneside Council who told him they were investigating it.
Coun Milburn added: “It could just be a bit of the land has fallen through, but if that’s the case, there’s not much underneath it.
“I also wondered if it was to do with the waterworks, which the water company are looking into.
“Another theory I had is that it could be part of a mine that we don’t know about.
“Any of them could be true in theory, which means there is potential for more subsidence.
“I hope that isn’t the case and the investigations find a simple answer and it can be filled in.
“But until then, I’d urge anyone walking up here to be extra careful.”
The waterworks were opened in 1863 and were built to exploit the reserves of clean fresh water that lay trapped in permeable limestone 258ft below ground.
The resulting reservoir was later covered with a large concrete dome, then believed to the biggest of its type ever constructed, which is still in place today.
A Northumbrian Water spokeswoman said: “The hole was reported to us on Friday and we went to investigate then.
“It is not an exposed manhole and appears to be erosion.
“There are no water mains or drains in the vicinity so Northumbrian Water has no further involvement.”
South Tyneside Council confirmed they were looking into who the land belongs to before any further action is taken.