What was thought to be the wall of a tower has turned out to be a road which ran across the inner bailey and shards of pottery, clay pipe and glass bottles have also been uncovered.
A team of archaeologists are mid-way through a two-week excavation at the site in a bid to discover what exactly is buried in the centuries-old soil.
Dr Nigel Baker, who is leading the dig said: "What we think we have is a road - basically the main drive coming in to the core of the inner bailey.
"The road has been cut away by an ancient pit probably for planting trees or something like that.
"What is exciting is that the geophysics that we had done at the beginning was half right and half wrong.
"Half right in the sense that what we have we have a band of hard resistance material and they thought that what we had here was the ruins of buildings and we have actually established that the hard material is a road surface."
"We have had some good objects out, the prize find is a glass seal which would have been on the front of a wine bottle. It has the arms of the Corbett family on it. We know that the Corbetts were associated with this castle in the 16th century so it's quite a nice find to have. It's part of the domestic rubbish which has been floating around in the topsoil."