Remains of Northampton's medieval castle have been unearthed on land earmarked for a new £20m railway station building in the town.
A stone wall has been discovered beneath a car park on Black Lion Hill, the site of the station redevelopment.
Senior archaeologist Andy Chapman said the find helped tell a "little bit more" about the castle's story.
Northampton Borough Council said the development, due to start next year, would still go ahead as planned.
The team from Northamptonshire Archaeology only had to dig about 3ft (90cm) down to discover evidence of what was on the land before the car park.
"We found the old cobbled surface of the old station yard," said Mr Chapman.
Anglo Saxon materials
"Beneath that we came on to these nice brown soils, all undisturbed, and beneath those we uncovered this stone wall.
"All the pottery at that level is mediaeval, so we've definitely got something that is associated with the old Northampton Castle."
Built in the 11th Century, Northampton Castle was situated on part of the current station site.
Part of the castle site was bought by London & North West Railway in 1852 and experts believe many of the remains were destroyed over time as the railway developed.
Mr Chapman said he had not expected to find much from the dig and was pleased to have found evidence of materials from the Anglo Saxon period - before the castle would have been built.
"From this trench it's difficult to say what we've got but it's a small building set up against the side of the castle.
"I'm surprised how much we've got surviving and what good condition it's in.
"We don't know a great deal about the castle - it was destroyed in the 19th Century with only a very basic record."
Chris Garden, director of regeneration at West Northamptonshire Development Corporation, said: "Clearly, it is very important that the development of Northampton Station respects the rich history and heritage of the site.
"The archaeological assessment is a key step in our preparations and will help to inform how we deliver the new and improved station."