Arholma is an island

Island

An island or isle is any piece of sub-continental land that is surrounded by water. Very small islands such as emergent land features on atolls can be called islets, cays or keys. An island in a river or lake may be called an eyot , or holm...

 in the north eastern part of the Stockholm archipelago

Stockholm archipelago

The Stockholm archipelago is the largest archipelago of Sweden, and one of the largest archipelagos of the Baltic Sea.-Geography:The archipelago extends from Stockholm roughly 60 kilometers to the east...

 in Norrtälje Municipality

Norrtälje Municipality

Norrtälje Municipality is a municipality in Stockholm County in east central Sweden. Its seat is located in the city of Norrtälje....

.

Arholma has about 60 permanent residents. But like so many other island outside Stockholm, it gets an influx of residents in the summer raising the number of residents to 500.

It houses a 10,5 cm coastal battery

10.5 cm tornautomatpjäs m/50

The 10.5 cm tornautomatpjäs m/50 was the first modern weapon system designed for the Swedish coastal artillery. Development started in the late 1940s, and construction of 6 gun installations based on this system was offered by Bofors in 1950...

 from the cold war

Cold War

The Cold War was the continuing state from roughly 1946 to 1991 of political conflict, military tension, proxy wars, and economic competition between the Communist World—primarily the Soviet Union and its satellite states and allies—and the powers of the Western world, primarily the United States...

which has been turned into a museum. The island has two Hostels and regular passenger traffic as well as a port for visiting private boats.