Muskö is an island in the southern part of Stockholm archipelago. It has been best known for its naval base, much of which was closed 2004. There is a small urban area which had 261 inhabitants in 2010. The island is part of Haninge Municipality, Stockholm County, Sweden.Access to the mainland is by two bridges, as well as a road tunnel, under waters of the Baltic Sea, with a length of 2895 meters.