Sixty metres under a chalk hillside in the Danish countryside, for the first time curious visitors are being offered tours of the top secret bunker built at the height of the Cold War to shelter Denmark’s monarch and government from nuclear war.

Nearly 300km from Copenhagen on the island of Jutland, the bunker was maintained secretly, with local residents unaware of its existence until it was declassified in 2012.

From February, visitors can take a tour of the 5500 square metre facility, which is still fitted with its original furnishings, from hospital beds, medical supplies and communication equipment to designer Arne Jacobsen chairs in the cafeteria and cabinet room.

NATO member Denmark built the shelter over five years and named it REGAN-Vest, from the Danish for ‘government facility – west,’ on its completion in 1968.

It was designed to house 350 people, including Queen Margrethe and cabinet as they tried to continue governing, post nuclear-apocalypse, as well as doctors, nurses, journalists, priests and technicians to help run the state.

“They actually thought that the Third World War was a possibility and a Third World War with the use of nuclear weapons, so they built this government bunker underneath a chalk hill here in Oplev, it’s 60m below the surface of the hill," curator of the bunker and the adjoining museum, Ulla Varnke Egeskov said.

After the collapse of the Soviet Union, the Danish government started to include REGAN-Vest in fewer exercises and finally declassified and decommissioned it officially in 2012, after which a decade-long project to document the facility and its fittings and then open it as a museum was launched.

A tour of the bunker takes around 90 minutes, taking in the shelter’s different levels that also housed accommodation for the monarch.

When they return to the surface, guests can also visit the house of the bunker’s chief machinist and family, behind which the facility was hidden. The machinist was under orders to keep the facility top secret.

“People that didn’t know much beforehand were blown away by the amount of detail,” said Line Bach Haga, who works at the museum next to the bunker.

The museum includes exhibits looking at Denmark in the Cold War, including pamphlets distributed to households explaining what to do in case of conflict, and artifacts from Hiroshima.

“I think it’s very important to see what the past was,” Jesper Arbo Frederiksen, a paramedic and local politician with the Social Democratic Party said after visiting the bunker. “And also in light of the war in the eastern Europe, I think it’s important to know these things."