Karlskrona was founded in 1680 by King Carl XI as the new home for the Swedish fleet. At the same time the construction of the naval fortress at Drottningskär on the island of Aspö began. This fortress, together with the fortress at Kungsholmen, was supposed to defend the main entrance to Karlskrona. Originally the fortress at Drottningskär was the main facility, but later that role was taken by Kungsholmen since the potential for expansion was greater there. The fortress at Kungsholmen, which here can be seen to the east, is the world's oldest continuously fortified military installation as it has been manned since the 1600s.
The naval fortresses at Drottningskär and Kungsholmen are both part of the World Heritage the naval port of Karlskrona.