Secret Underground Bases | The Musko Facility Declassified ✔️

Deep beneath a granite mountain, making it almost impervious to destruction is one of the world's largest underground military facilities. Known as the Musko facility, it's located on the island of Musko in Sweden.

As most secret underground bases, the Musko facility was kept top secret until 2004 and knowledge

of it was very limited until it was declassified. Built as a military naval base in the 1950's parts

of it are still operational today.