Suomenlinna, until 1918 Viapori (Finnish), or Sveaborg (Swedish), is an inhabited sea fortress built on six islands (Kustaanmiekka, Susisaari, Iso-Mustasaari, Pikku-Mustasaari, Länsi-Mustasaari and Långören), and which now forms part of the city of Helsinki, the capital of Finland.
In 1747 the Swedish Diet made a decision to fortify the eastern border and to establish a place d’armes on islands outside Helsinki. France, with which Sweden had a military alliance, financed a great part of the construction during the first decades.
Sveaborg was the largest construction project in Sweden in the 18th century. It was constructed under the supervision and direction of Lieutenant-Colonel Augustin Ehrensvard, assisted by the best Swedish engineering and mechanics experts. The fortress was constructed by soldiers in the regular army from all over Sweden and Finland. At its height, the construction crew totalled more than 6500. When Ehrensvard died in 1772, the fortress was virtually ready for use. The overall plan was revisecf in 1774.
European power politics also determined Sveaborg’s fate. In the war of 1808-1809, which was a direct consequence of the treaties between Napoleon and Alexander I, Russia occupied Finland. Sveaborg surrendered and became a Russian garrison for the following 110 years. At the turn of the century there were about 4000 Russian soldiers in Sveaborg. The fortress remained in the state it had been under Swedish rule until the bombings during the Crimean War in 1855, when the British and French Navies ·fired on the fort. In the repairs and modernisation , undertaken after .that, some of the damaged buildings were torn down or made lower and a new coastal defence line of earth banks was constructed.
Before the First World War, Sveaborg, mainly serving as a depot area, formed part of the defence scheme, “Peter the Great’s Sea Fortress”. The intention was that Sveaborg, together with Tallinn, would block off the entire Gulf of Finland and guarantee the security of St Petersburg, the Capital of Russia. After Finland became independent in 1917, Sveaborg became a Finnish garrison and was renamed in Finnish as Suomenlinna. It served as a prison camp after the Civil War in 1918-1919. Suomenlinna was in military use for the last time during the Second World War when it served as one of Helsinki’s air surveillance centres. It served as a garrison until 1972. Its use for tourism and recreation began on a larger scale after 1963 .