Suomenlinna (Finnish: [suomenlin]; until 1918 Viapori, Finnish: [viapori]), or Sveaborg (Swedish: [svborj]), is an inhabited sea fortress built on eight islands about 4 km southeast of the city center of Helsinki, the capital of Finland. Suomenlinna is popular with tourists and locals who enjoy it as a picturesque picnic site. Originally named Sveaborg (Castle of the Swedes), or Viapori as referred to by Finnish-speaking Finns, it was renamed in Finnish to Suomenlinna (Castle of Finland) in 1918 for patriotic and nationalistic reasons, though it is still known by its original name in Sweden and by Swedish-speaking Finns.

The Swedish crown commenced the construction of the fortress in 1748 as protection against Russian expansionism. The general responsibility for the fortification work was given to Augustin Ehrensvrd. The original plan of the bastion fortress was strongly influenced by the ideas of Vauban, the foremost military engineer of the time, and the principles of the star fort style of fortification, albeit adapted to a group of rocky islands. Famous for these bastion fortifications, Suomenlinna became a UNESCO World Heritage Site in 1991.During the Finnish War, Sweden surrendered the fortress to Russia on 3 May 1808, paving the way for the occupation of Finland by Russian forces in 1809, and the eventual cession of Finland to Russia at the conclusion of the war. Russia held the fortress until Finnish independence in 1917. Finland then managed Suomenlinna through the Defense Department until turning most of it over to civilian control in 1973.



The Finnish War (Swedish: Finska kriget, Russian: Финляндская война, Finnish: Suomen sota) was fought between the Kingdom of Sweden and the Russian Empire from 21 February 1808 to 17 September 1809. As a result of the war, the eastern third of Sweden was established as the autonomous Grand Duchy of Finland within the Russian Empire. Other notable effects were the Swedish parliament's adoption of a new constitution and the establishment of the House of Bernadotte, the new Swedish royal house, in 1818.