Experts recently uncovered a nuclear bunker from the Cold War - located, strangely, on the grounds of a medieval castle in England.
The bunker was decommissioned and sealed in 1968, British news agency Jam Press reported.
The hideout was presumed lost until archaeologists from English Heritage recently pinpointed its location at Scarborough Castle in North Yorkshire.
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The tiny space measures roughly 15 feet, 6 inches long and 7 feet, 6 inches wide.
The bunker was intended for volunteers of the Royal Observer Corps (ROC), who would monitor and report on nuclear blasts in the event of war.
The lookout post has remained a mystery since its closure, with online sleuths suggesting it was buried somewhere between the castle and the North Sea.
Britain was once dotted with around 1,500 ROC posts, a little-known Cold War network, said Kevin Booth, senior curator at English Heritage.
"Wherever you lived in Britain, you were probably no more than a few miles from an ROC post," he told Jam Press.
Booth added, "It seems strange to have a Cold War bunker built inside Scarborough Castle, but in many ways, it is a perfect location."
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The expert cited the bunker's strategic position on a headland used since the Bronze Age, including during the Roman period and the Middle Ages.
He described it as a "1960s concrete bunker watching for Armageddon."
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Booth added that researchers were keen to locate it and "reopen it [to] see what was inside."
"Old mapping gives a sense of where it might be, but it really comes down to survey - looking under the ground with radar to find the big black blob that is a concrete structure," he said.
The bunker remains sealed for now, and researchers found that it had around six feet of water in it.
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They hope to open it in the future once it is safe to access.
The find adds to a growing list of recent archaeological discoveries across England.
Excavators recently found four-wheeled wagons from the Iron Age near the village of Melsonby in Yorkshire - the first such discovery in Britain.
Officials also recently announced they had identified a 2,000-year-old coin unknowingly used as bus fare in Leeds.
