Here’s what you’ll learn when you read this story:

• Archaeologists discovered a long-forgotten Cold War bunker at Scarborough Castle in England.
• The Royal Observer Corps used the bunker for just five years during the 1960s as an observation post for nuclear blasts, but it was sealed and lost to time in 1968.
• With over 1,500 observation posts across the United Kingdom, there could be thousands more bunkers ripe for discovery.

The Cold War impacted many more countries than just the United States and the Soviet Union, causing NATO allies to fret over nuclear fallout enough that some countries made significant efforts to protect themselves against it. For example, Britain’s Royal Observer Corps, a civil defense organization with 20,000 volunteers, created over 1,500 observation posts during the Cold War, including bunkers designed to withstand nuclear attack. Archaeologists have just discovered one such bunker at Scarborough Castle in northeast England.

The site of Scarborough Castle is quite the historical hodge-podge, containing remains of a Roman signal station in addition to an Anglo-Saxon church and the castle itself, which was built in the 1130s. Officials from the Royal Observer Corps added a more modern structure in the form of a Cold War bunker in 1963 as part of a network designed to detect explosions in the event of a nuclear war.

The post lasted just five years and after it was sealed and buried in 1968, the location and condition of the bunker were lost to time. Until now, that is. Archaeologists from the charity group English Heritage, thanks to funding from the National Lottery Heritage Fund, followed analysis of existing data and combined it with a newly commissioned ground survey to identify the likely location of the Scarborough site. The team then excavated in early March and within two days had uncovered the sealed entrance. The team lowered cameras into the chamber below to assess its condition and plans to further investigate to learn more about the site.

“Wherever you lived in Britain, you were probably no more than a few miles from an ROC post—yet few people knew they existed,” Kevin Booth, head of collections at English Heritage, said in a statement. “It seems strange to have a Cold War bunker built inside Scarborough Castle, but in many ways, it is a perfect location: this headland has been an observation post for thousands of years, from a Bronze Age settlement to a Roman signal station, medieval castle, World War I gun battery and, here, a 1960s concrete bunker watching for Armageddon.”

The ROC bunkers were designed to withstand nuclear attack, and each post had near-identical specifications that included communications facilities and bunkbeds for those fortunate enough to escape there. A York Cold War bunker that operated until 1992 was previously restored by English Heritage and is now the organization’s most modern attraction.

The bunkers feature a control room with the original monitoring devices, a “hot bed” dormitory where up to 60 staff could sleep, communications rooms, and a sewage ejector unit. The windowless site had an air-filtering system and a water supply reserve that lasted just 30 days.

“It’s really exciting that this lost bunker has been uncovered by the team working on this project marking 100 years of the Royal Observer Corps,” Helen Featherstone, director of the northern England portion of The National Lottery Heritage Fund, said in a statement. “This find builds on our understanding of their story and shines a spotlight on their important work protecting the UK.”