Archaeologists investigating land below a proposed building site at Stafford College are hoping to uncover the area's medieval past.
Proposals for a new arts department, sports hall and extension to the nursery at the college have been submitted to Stafford Borough Council.
The team, from Birmingham Archaeology based at Birmingham University, is investigating the site, which is currently a car park.
It is hoping to find Anglo-Saxon and medieval remains at the site on Broad Street.
The team has already uncovered fragments of pottery and what might prove to be the first recorded trace of the original defensive ditch thought to circle the old town.
County council archaeologist Chris Wardle said: "Some very significant archaeology on the site may help to answer questions about the medieval town.
"The excavation has revealed part of a ditch and because of its location we may be looking at the first part of that defensive boundary."