Brims Construction were carrying out refurbishment work at Oxbridge Lane Primary in Stockton-on-Tees when they found a strange concrete building, a World War 2 air raid shelter hidden beneath the playground.
Site manager Jason Harrison described excavating and uncovering the distinctive arch shape before realising it was a shelter.
Headteacher Lauren Amerigo said it was an “incredible discovery” that had fascinated the children, some of whom had been studying the era at the same time the shelter was revealing itself.
Mr Harrison said: “This is the first time I’ve found anything like this. We didn’t know it was there.
“We were getting ready to connect some pipework and we uncovered the concrete top.
“As we excavated down a bit we could see that it was a sort of bell shape.”
The bunker is approximately 24ft long and had partially flooded with water which has since been drained.
‘Hide under table’
The discovery has thrilled Year Six students, including 11-year-old Skyler who said: “It was exciting to learn we had an air raid shelter under the playground, but I wasn’t very surprised.
“Our school is quite old, but I didn’t expect it to be so well-preserved.
“It looks just like one of the shelters we saw when we visited Eden Camp Museum.
“My great-nana and great-grandad were alive during the war, but they didn’t have a shelter, they used to hide under the kitchen table.
“We learned that boys and girls would often have separate shelters and I think it might be the boys’ one because there is an old sign on a wall nearby that says ‘Boys’.”