HSwMS Sundsvall entering one of the openings to the naval base

The Swedish Navy’s headquarters is returning to a vast underground naval base beneath Muskö in the Stockholm Archipelago in response to a perceived threat of a Russian attack. The vast underground cold war fortress can shelter warships and submarines and was designed to withstand a nuclear blast. The facility includes two shipyards and is connected to the mainland by a series of causeways and a tunnel.

The Guardian quotes Niklas Granholm, a senior analyst at the Swedish Defence Research Agency, saying “The move is based on the calculation that the Russians could use powerful weapons which demand the level of protection that only Muskö can provide.”

While the island was used by the Swedish navy as a base since the 1500s, construction of the underground base began in 1950 and was completed in 1969. During the construction, about 1.5 million tons of rock were removed. During the Cold War, the underground facility was kept secret. The Swedish Navy used the base until around 2004. 

“The Muskö base is unique from a fortification perspective, it is an underground area as big as the old town in Stockholm,” said Rebecca Landberg, head of communications for the Swedish navy.

“The naval command must have resilience and function even under attack, so Muskö is the best option … the armed forces need to adapt their operations to meet the challenges posed by the deteriorating external environment.”