Mariaberget shelter in Västerås is one of the largest in Sweden. Built on two levels within the granite bedrock, it could have accommodated up to 5,500 shelterers. Construction took about five years, with completion in 1958. The two-level bunker found peacetime uses, including sports training, music studios and a theatre.
In the event of activation, it would have been sealed with immense blast-proof doors weighing around 20 tonnes. The facility was designed to be self-sufficent in water, power and heat for the period of isolation.