Karstenia fortress located in the municipality of Bohuslän, on the island of Marstrand, in the 19th century was known worldwide as one of the strongest and most fortified in Europe.

After 1658 peace was concluded in Roskilde, Bohuslän was ceded to Sweden. The city has long been a major trading centre, and due to the fact that the port during the year, almost never cold here and is part of the Swedish fleet. To protect Marstrander, Charles X decided to build on the island fortifications. To draft a future of the fortress was assigned to the engineer Johan Verschelde. Initially, in 1658 on the island were erected makeshift wooden building, thanks to which in 1659 the Swedes managed to repel the attack of Norwegian troops. In 1666 began construction of the stone fortress. In the years 1780-1783 construction work was carried out in the tower Carlsten, the results of which she could serve as a beacon. Moreover, it was the first lighthouse in the world with a rotating mirror device.

Almost from the first years of its existence Karstenia the fortress served as a prison for political prisoners and dangerous criminals. For example, here for 26 years contained the most famous Swedish burglar and adventurer Lasse Maya. Despite the fact that by 1855, all the prisoners were moved to Gothenburg, Carlsten for a long time was known as "fortress of the prisoners".

Due to the fact that in the second half of the 19th century steam ships almost completely replaced sailing, and the war with Denmark became less likely, the importance Karlstejnska fortress fell sharply. That is why it was decided to move the artillery regiment from Carlsten in Vaxholms and Karlsborgs fortress. In 1906-1937, part of the premises of the fortress was in use Mastrangeli school Jung. The use of the fortress for defensive purposes was finally discontinued in 1993.