The Karlsborg Fortress is located in Karl Borg in the Swedish province of Västra Götaland County and the historic province of Västergötland . It was built between 1818 and 1909. After the Napoleonic Wars and the loss of Finland , a new defense doctrine was adopted, which - in the event of an attack - was based on the abandonment of peripheral areas and a central defense of Sweden. In the event of war, the royal house, government and Reichstag as well as the country's gold reserves were to be relocated to a central fortress. As a fortress town of the peninsula was Vännäs udde in Vättern chosen because the planned here Gota Canal should flow into the lake.
Construction of the fortress began in 1819. The fortress was to house a garrison of 6,000 men and a further 8,000 to 10,000 people on an area of almost 100 hectares. By 1830 the ramparts were largely finished, but the question of how the fortress on the land side should be built was still unsolved. During an inspection by King Karl XIV. Johann in 1832, the fortress was named after him. After an extensive study trip to Europe, fortress architect Johan af Klen presented plans based on the Prussian Fort Winiary (now Poznań ) as a model . A 678 meter long, two-storey, brick building with casemates, loopholes and three mighty towers was built between 1845 and 1869. In the middle was the garrison church, which was also intended as a meeting place for the Reichstag.
When this fortress was inaugurated in 1869, the defense doctrine of the central defense was already out of date. The fortress's role of crisis and reserve capital was no longer relevant, but the fortress continued to be expanded. However, the technical development in the field of artillery in the second half of the 19th century also meant that the fortress was completely outdated in 1909, when it was finally completed, and exposed to modern artillery without protection.
In 1928 it was abandoned as a defense structure, but still serves as a barracks and warehouse today. During the Second World War it was also the depot for the country's gold reserves.
Inside the fortress is a small town with interesting buildings from the second half of the 19th century, such as the Royal Villa in the Empire style and the garrison hospital and a museum. The fortress is open to the public. Since 1935 it has been under state protection as Byggnadsminne .