The town centre pub's management and regulars attribute some of the strange goings-on at the venue to its past.
Ghostly figures appearing and glasses shattering and wobbling for apparently no reason are among the incidents encountered in recent months.
Pub regular Geoff Chapman, 50, said: "There's all sorts of funny things that go on in there."
Landlord Derek Barnes said: "One night we were sitting in the pub after closing time and this figure just appeared from the part of the wall where the old entrance was.
"He was wearing what looked like a tweed jacket and just walked across the pub then disappeared.
"I said to Geoff, who was with me, did you see that?
"And he said 'I didn't want to mention it because it seemed silly, but I definitely saw something'."
The dozen brick-walled rooms, not large enough for an adult male to stand in, now form the cellar of the pub and contain barrels of beer and other supplies.
Men destined for the gallows during the 19th Century were left in the tiny cells for the night before their execution and the room even had a dedicated pathway to the nearby courthouse and former police station.
Mr Chapman added: "I saw the shape of something and thought 'what the hell was that?'
"I thought it must have been somebody else in the pub, but we were the only people in there."
Other unexplained incidents include a handled pint glass hanging above the bar exploding and the regular appearance of orbs.
Mr Barnes, 52, who has been in charge of the St Georges Place inn for five years, said: "Nobody was anywhere near the glass but it just shattered as if somebody had shot it, luckily nobody was hurt."
Orbs are believed by many who study paranormal activity to be ghosts in the form of balls of light.
Mr Chapman said the child of a former landlord had reported seeing ghosts in a bedroom above the pub.
A group of regular customers is set to take part in an all-night stakeout for ghosts on April 27 in an effort to capture paranormal activity.
Story: Gloucestershire Echo