Archaeologists are investigating some unusual building features found inside Bodiam Castle, East Sussex.
Visitors look at the stonework discovered at Bodiam Castle
Earth was being cleared in the Great Hall ruins when stonework was found, including clay tiles and rubble.
Some ruins may date from the time the castle was semi-demolished but a wall and a circular feature are a mystery.
County Archaeologist Casper Johnson and experts from the National Trust are racing to log the find before the floor area is covered with a gravel base.
Until recently, grass had covered the floor of the 14th Century dining hall but scaffolding used to make repairs to the hall's huge window had churned up the area.
'Slighted' by Cromwell's troops
Castle owners, The National Trust, decided to mark out the floor area with gravel, and a layer of topsoil was being dug away in preparation when they struck stone on Friday.
The castle's staff believe the rubble and tiles probably date back to the day it was "slighted" by Cromwell's troops.
The wall and the mysterious circular feature could be either an 18th Century gardener's cottage or even part of the original medieval hall.
The moated castle, near Robertsbridge, was built in 1385 by Sir Edward Dalyngrigge when the French were raiding the Sussex coast.
The interior has been exposed since the roof was removed in the English Civil War, more than 350 years ago.