As the warnings continue of an increasing nuclear threat from Vladimir Putin, many countries are asking themselves if they are prepared for the fallout.

Luckily, Germany’s capital of Berlin has been prepared for nearly 50 years, as an extension to its U-Bahn subway had a Cold War bunker to protect civilians incorporated into its design, concealed behind a nondescript steel door next to the platform.

The well-preserved bunker has remained ready, just in case. Storage rooms contain bunk beds, thin blankets and polyester suits for 3,500 people, along with 70 bassinets for infants and several stacks of body bags.

The bunker at the Pankstrasse (Pankstraße) subway stop in a working-class neighbourhood of Berlin is part of a spaghetti network of intact underground shelters dating to the city’s tumultuous years during the 20th-century.

The Pankstrasse bunker would be able to house around 0.1 percent of the 3.4 million-strong population of Berlin for up to 14 days.

At one end of the Pankstrasse bunker are decontamination, ventilation and filtration plants, among other services, while the other end provides facilities for occupants, including an emergency kitchen. Supplies to last inhabitants the two weeks would include two toilet rolls, a bar of soap, a towel, a bowl and a cup.

In the event of activation, gas-tight doors would be closed in the running tunnels at each end of the platform. This would only be done only after two trains were parked at the platforms to provide additional seating.

Siemensdamm station on line U7 had a similar ‘multi-purpose’ function.

During World War Two, Berlin had an estimated 1,000 underground bunkers to shield its residents. By the end of the war, more than two-thirds of them had been destroyed. Many of the others were later sealed off or forgotten.

Beginning in the 1970s, the West German government began a program to refit some of the bunkers as nuclear fallout shelters. The refurbishing was meant to reassure the public that the city had a viable civil defence plan in case World War Three broke out.

In the end, however, there was enough fallout shelter space for only about 27,000 West Berliners out of a 1970s population of about two million. Far fewer shelters were opened in East Berlin, with nearly all the beds reserved for the Communist Party elite.

“Today, if there is some kind of war, they could still be put to use,” Kay Heyne, a Berlin Underworlds tour guide, told NBC News, all the way back in 2007 when the threat of a nuclear war did not seem nearly as likely.

“We had to agree to keep this bunker in operating condition, in case of war.”