A mysterious underground lake lies hidden beneath the city centre - and most people don't even know it is there.
Images shared with the ECHO back in 2017 offered a previous unseen look at the secret world which lies beneath the city's business district. The spooky pictures were taken by an engineer carrying out maintenance work for the council beneath the city centre.
One picture appears to show a hidden vault, which seems to go back for some distance, with stone arches which stand below street level. It is believed this hidden world can only be accessed via a small tunnel, which opens up to reveal the huge vaulted area filled with water.
