LUCERNE, Switzerland — From the outside, the Sonnenberg nuclear bunker looks innocent enough: its entrance is in the middle of a children's playground. But past the seesaws and swing sets, carved into a hill, is a thick blast-proof door that, when opened, exposes a narrow, well-lit tunnel that gently descends as far as the eye can see.

Sonnenberg Bunker guide Zora Schelbert walks slowly down the tunnel toward the main structure of the bunker, built in the 1970s, during the Cold War, to house 20,000 people in the event of a nuclear war.

"Back then, 20,000 people constituted a third of our city's inhabitants," says Schelbert. "So every third person in the city of Lucerne was once supposed to be sheltered in this bunker."

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The entrance to the nuclear bunker underneath the University of Bern's History Department building.

If a nuclear war between the U.S. and the Soviet Union were to happen, Swiss officials reasoned at the time, Switzerland — an historically neutral nation — would likely not suffer a direct hit. But it would be in the path of nuclear fallout from its non-neutral neighbors. So they supplied diesel-powered generators that had enough fuel to power this bunker for two weeks.

"So after two weeks, no more food, no more water, no more power," says Schelbert. "And today, civil defense also says that the duration of stay depends on what the problem is outside. And as we can see currently in Ukraine or Israel, this makes total sense because as long as it's a conventional war, people seek shelter temporarily and then you can leave again."

Instead of scrapping its nationwide network of bomb shelters after the Cold War ended, Switzerland doubled down and kept building them, guaranteeing every one of its 9 million citizens a bomb shelter space, just in case. The country has more than 370,000 nuclear bomb shelters.

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Daniel Jordi, vice director of Switzerland's federal office of civil protection, says in 2011 when Switzerland's parliament was debating whether to scrap all its bomb shelters, lawmakers voted to maintain the network. The vote took place after Japan's Fukushima Daiichi nuclear power plant melted down following a massive earthquake and tsunami.

"There were a couple of political discussions, especially in 2010, 2011," recalls Daniel Jordi, vice director of Switzerland's federal office of civil protection. "There was a discussion in the parliament to finish with the system."

But just as the national parliament was debating whether to scrap all of the country's bomb shelters in 2011, the Fukushima Daiichi nuclear power plant in Japan melted down after a massive earthquake and tsunami. "And they came to the conclusion that it's good to have those shelters as a national reserve to protect the people in the real emergency," Jordi says.

That means every residential building in Switzerland is required to either build a bunker with proper blast doors and ventilation systems or developers have to earmark funds for a nearby bunker maintained by the state. Swiss citizens have to pay an upfront fee between $1,700 to around $3,500 for the maintenance and construction of these shelters.

In peacetime — which, due to its neutrality, is the norm in Switzerland — these bunkers are turned into wine cellars, saunas or, in the case of the University of Bern, storage.

Silvia Berger Ziadduin is an expert on the history of Switzerland’s network of nuclear bunkers, and she gives a tour of the University of Bern’s underground bunker. She says bomb bunkers are rooted in the idea that this tiny alpine nation has, for more than a century, served as an island of calm surrounded by a sea of chaos. — Rob Schmitz / NPR
Silvia Berger Ziauddin, an expert on the history of Switzerland's network of nuclear bunkers, gives a tour of the University of Bern's underground bunker. She says bomb bunkers are rooted in the idea that this tiny alpine nation has, for more than a century, served as an island of calm surrounded by a sea of chaos.

History professor Silvia Berger Ziauddin shows off a foot-thick door made of reinforced concrete, the entrance to the nuclear bunker underneath her department's building. Berger Ziauddin, an expert on the history of Switzerland's network of nuclear bunkers, says bomb bunkers are rooted in the idea that this tiny alpine nation has, for more than a century, served as an island of calm surrounded by a sea of chaos.

"It was an idea already developed in [the] First World War, actually," she explains. "And then in the Second World War, it was the same island metaphor that was developed again. And in the Cold War, the island metaphor was transposed to the nuclear shelter."

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This is a classroom for children in the Sonnenberg bunker. Many students spend a week learning about these bunkers as part of a civil defense-centered curriculum.

Berger Ziauddin says the Swiss government cultivates this idea through the country's schools. Each year, she says, many students spend a week learning about these bunkers as part of a civil defense-centered curriculum, "where you have to draw civil defense shelters, you have to watch civil defense movies, you have to go to the shelter and eventually sleep in the shelter for one night," she says.

Berger Ziauddin says at the end of the week, kids present their drawings to their classmates. "But then also, kids also talked about their drawings and said, 'OK, in the upper level of my drawings there is destruction and death and chaos, and underneath, there is warmth and security and there is the shelter and the family and the pet and the mother working and the father is reading,'" she says. "And this imagery is very persistent for kids."

But Berger Ziauddin also says the reality of life in a nuclear bunker would be a far cry from how Swiss children imagine it.

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The hospital in the Sonnenberg bunker is equipped for surgeries and other compelx medical procedures.

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This is the entrance to the hospital in the Sonnenberg bunker.

At the Sonnenberg nuclear bunker beneath Lucerne, Schelbert, the guide, walks past the bunker's hospital with bright green walls — a stylistic holdover from the 1970s — to the fourth level of the bunker, a security station complete with three prison cells, all painted bright yellow.

"It's 16 spots for 20,000 people," she says. "And over the last two decades, doubts then were raised as to whether this would have been enough, given the circumstances that led to people entering. So that's why I think it's fair to say that the size of the facility and the problems that come with such a big mass of people, be it social problems, psychological issues, this can be considered one of the factors that contributed to downsizing."

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Sleeping accommodations inside the Sonnenberg bunker in Lucerne.

And that's part of the reason why in 2002, Switzerland's government reduced the Sonnenberg bunker capacity from 20,000 to just 2,000. Its floors filled with bunk beds, a prison and hospital, all deep underground, have been repurposed over the years as overflow housing for refugees, asylum seekers and the homeless.

It's a use that has been criticized by organizations that help these populations. Some asylum seekers have protested against being housed here.

It has never been used for its original intent: to protect people from nuclear fallout. But the Swiss government continues to spend tens of millions of dollars a year to maintain it and hundreds of thousands of other bunkers throughout the country — just in case.

Esme Nicholson contributed to this report from Berlin.

Tagged: nuclear war

Switzerland is a neutral nation but has more nuclear bunkers than any country in the world