The Kungsholmen stronghold on an island on the fairway into Karlskrona started to be built already in 1680, and together with the Drottningskär citadel on the other side of the strait it was supposed to defend the naval port in Karlskrona that was built at the same time. The stronghold has over the years gone through extensive rebuilding and expansions to meet new defence technological threats.
The parts that are of most interest are the north redoubt, the donjon, the main powder magazine, the harbour and the park. The north redoubt is a closed bastion, later rebuilt into a defensive bulwark designed to protect the stronghold from the north. The donjon is the principal defence structure, mainly designed to protect the stronghold from an attack from land. The powder magazine, which is the oldest building of the stronghold, was finished in 1736. The boat harbour is a round dock intended for smaller boats. It used to be closed every night by an outer door and an inner gate. In the park, which was laid out in the 1870's, different southern trees, often brought home from the navy's expeditions, are well protected by the ramparts.
The Kungsholmen stronghold is still manned by the military and is used as a training camp for the Coastal Artillery. It is not allowed to visit the stronghold on your own, but guided tours are arranged by the Tourism information office.