Finland’s interior ministry reported that after finishing an inventory of its existing bomb shelters in response to neighboring Russia’s invasion of Ukraine last year, the country discovered it has 50,500 of them.

After repelling a Soviet Union invasion attempt during World War II, Finland continued to prepare for the prospect of a conflict with Russia and in April made a historic security policy U-turn by joining NATO.

The wary Nordic country made the construction of emergency shelters mandatory under apartment blocks and office buildings as early as in the 1950s, which explains their current high number.

The government’s census concluded that the Nordic nation of 5.5 million people has some 50,500 bomb shelters that can fit 4.8 million inhabitants in them in case of an emergency or an attack, the ministry said.

It also found that 91% of the shelters are robust enough to sustain an attack conducted with conventional weapons, while 83% are equipped to also provide shelter from gas emissions or nuclear emergencies.

“At the same time, it must be stated that in a small number of shelters there are faults that prevent them from being put into use within the 72 hours required by law,” project manager Ira Pasi of the interior ministry said in a statement.

The shelters are equipped with ventilators, impervious doors, stackable beds and even dry closets, as required by the latest law that dates back to 2011.

During peacetime, some of the underground shelters house swimming pools, sports centres or – as in the very north of the country – a Santa Claus theme park.

The shelters are maintained by each building’s owners and the government called for their proper upkeeping.

“Over the decades, Finland has built a civil protection infrastructure worth billions of euros, which is worth taking care of,” Pasi said.