With its brightly coloured slides, trampolines and tunnels, the soft play area at the Hakaniemi Arena, near the centre of Helsinki, looks much like any other. The difference is that it lies 25m below ground in a cavernous space hollowed out of the Precambrian bedrock beneath the city, and is designed to withstand nuclear, biological and chemical attacks.
The clambering children may not realise it, but they are in one of the safest playgrounds on earth.
Most of the time, this is a family-friendly sports centre. Above ground, the only visible clue to its second identity is a small orange and blue triangle on the wall by the entrance that states: “VÄESTÖNSUOJA SKYDDSRUM”, or “defence shelter”. In the event of an emergency, the arena would revert to being the Merihaka bomb shelter, a subterranean living quarters where up to 6,000 people could exist for weeks, or even months…
Helsinki alone has more than 5,500 bunkers, with space for 900,000 people. Finland as a whole has shelter spaces for 4.4 million, in more than 54,000 separate locations.