For two millennia the Great Drain has carried the mineral-rich waters of Britain’s only hot spring from the Roman Bath in Bath to the nearby River Avon. The drain runs for nearly half a mile under the city but although parts of it are large enough for a man to walk through, it has never been fully explored.
Archaeologists will have their first opportunity to get inside the previously inaccessible sections of the Great Drain this month when engineers open it up for repairs.
A stretch of drain built long after the Romans is causing the difficulties. The extension was added when marshes were reclaimed from the Avon beyond the old city wall. It started to back up 18 months ago, causing a flooding risk in the city.