While investigating HM Prison Gloucester in Gloucestershire, England, ahead of planned redevelopment, archaeologists unearthed a castle wall dating back to 1110 A.D., just a mere centimeters beneath the indoor basketball court. Gloucester Castle, otherwise known as Norman Castle, is believed to be the first to have been built in Gloucester in the 12th century, reported The Week. Built from stone, it once had three chapels, two drawbridges, and royal chambers for the king and queen.

Archaeologist Neil Holbrook expressed surprise over the find, noting that the castle had been demolished in 1787 to build the prison on the site and the "walls had "never been seen in the last 200 years."

"I am surprised by what we found," he said, according to the Gloucester Citizen. "I knew there was a castle but I had expected more of it to have been destroyed."

He went on to describe the wall as a "massive structure" that was likely the "huge tower keep," which would have been used as city gaol (jail) before it was toppled.

"It would have been a powerful symbol of Norman architecture," he continued. "As you came to Gloucester you would have seen the Cathedral and the castle, which is representative of how important the city was in Norman Britain."

Gloucester Parliament member Richard Graham was quite happy to see the wall uncovered, exclaiming that it's an indicator of the city's heritage: "It is a real treat to be lucky enough to see the keep for the first time since 1790. The quality of the walls that they have uncovered is fantastic. We are still uncovering our history in Gloucester and this is another reminder of the rich heritage that the city has."

Following this discovery, archaeologists now believe that other parts of the castle may be underneath other buildings at the prison, leaving real estate developer City & Country Group, who bought the prison after it shut down in March 2013, to determine what parts of the castle will be preserved during construction on the site.