First sight of hidden River Roch bridges
11 December 2013 Last updated at 11:46 GMT
The River Roch was the lifeblood of Rochdale at the time of the Industrial Revolution, but in Victorian times it was covered over and forgotten about.
BBC North West Tonight reporter Mark Edwardson was given a one-off tour of the underground medieval bridges, which have remained unseen for a century.
They could now be uncovered in a £4.2m project funded by the Heritage Lottery Fund, Rochdale Council and the Environment Agency.