Finland has built a network of underground bankers to shield against nuclear and gas attacks.
The Nordic country has built 500 bunkers in the capital Helsinki which can hold hundreds of thousands of Finns in the event of a war or nuclear disaster.
The bunkers are connected by a vast network of underground tunnels stretching 200 miles and have enough space and beds to hold all of Helsinki’s 630,000 residents. Every bunker has two weeks-worth of food and water supplies.
Pictures taken by the Reuters news agency show one huge underground sports hall that can be turned into what the Government call a “civil defence shelter”.
In the event of an attack, citizens would descend into the tunnels through covert entrances on the streets above.
Construction of the bunkers began in the 1960s and successive governments have since invested in the tunnels.
One of the bunkers’ “preparedness” instructors Varautumisen Opettaja told the Mirror: “This door can take a blast of up to six bars of pressure, so even a nuclear bomb won’t break it.
“The second door is gas and chemical proof. So there could be bombs dropping above and yet children happily playing down here below.”
He added: “It’s all about showing that we can survive. And if anyone attacks us again, we will survive.”
Tomi Rask, a preparedness teacher at Helsinki City Rescue Department, told CNBC that that the bunkers also offered protection against “radiation and toxic chemicals”.
Pressed on why the country had built the bunkers, he said: “We have neighbours. And naturally the neighbours might cause us some immediate danger.”
Earlier this month, Finland applied for Nato membership to enhance its security following Russia’s invasion of Ukraine.
Mr Putin’s bloody campaign has prompted a surge of enthusiasm for joining the alliance, in a country previously committed to neutrality.
Finland and Russia have a troubled past and have fought several wars, most recently between 1940 and 1944 after Joseph Stalin’s Red Army invaded the country. Both countries share a 1,340km border.
While previously remaining neutral, Finland has a large defence budget and can muster a wartime army of 280,000 personnel, on top of 900,000 reservists.