Webjeff highfield uncovered the tunnels during a £1 million refurbishment plan to build luxury offices on the site.
The tunnels are thought to be around 250 years old.
Webmemories 463 uncovered stories of a network of tunnels that apparently ran from mount grace priory into the friarage in yarm (now yarm school) from where one.
Weban underground lost street of tiny homes has been revealed to be part of a wider network of tunnels.
Weba georgian townhouse in the center of town was slated for renovations, and in the process, the owner discovered a series of crumbling rooms and tunnels.
The underground dwellings, thought to be 250.
Webthis network of secret underground tunnels allegedly runs throughout the town, along the high street and even reportedly down to the river.