From the World Heritage inscription:
In the history of military architecture, the Fortress of Finland (Suomenlinna) is an outstanding example representative both of the general fortification principles of the period and of its specific characteristics.
In 1747, when Finland was part of the Swedish realm, the Diet in Stockholm decided to build a fortress to serve as the main base for the armed forces stationed in Finland. A group of islands close to Helsinki were chosen to be the site of the fortress, which was to be called Sveaborg, the ‘Fortress of Sweden’, and construction began in 1748. The purpose was to link and fortify several islands so that entry into the city’s harbour could be controlled.
The work began in 1748 under the supervision of the Swedish Admiral Augustin Ehrensvärd (1710-72), an artillery officer of aristocratic background in his mid-thirties. He adapted Vauban’s theories to the very special geographical features of Helsinki. Ehrensvärd’s original plan was to build a chain of linked fortifications across a group of islands close to Helsinki and to fortify certain strategic points on land around the town itself. The second part of the plan was never carried out, but by the time of his death in 1772 Ehrensvärd had produced the chain of forts, collectively called Sveaborg (Swedish Fortress), that were to protect the approaches to Helsinki. By the end of the century the construction work was virtually complete.
One of the main reasons for building Sveaborg was to help Sweden counter the ambitions of Russia, whose principal military base in the Gulf of Finland was Kronstadt, commissioned by Peter the Great to protect the city of St Petersburg and as the home port of a new Russian Navy to challenge Swedish maritime power in the eastern reaches of the Baltic Sea.
Although Sveaborg was operational at Ehrensvärd’s death, fortification continued. King Gustav III (1771-92) seems to have taken a close interest in the work. The fortress was occupied by the Russians after the war of 1808-9 (despite its reputation as being invulnerable); it was again strengthened and its name was changed to Viapori. Swedish power in the region gradually declined and in 1808 Sveaborg was surrendered to Russian forces. In 1855, during the Crimean War, Franco-British soldiers bombarded the fortress to no avail. However, reconstruction work and new construction were undertaken. Following Finland’s independence (1918), the name was changed a final time to Suomenlinna (Fortress of Finland). 6 km of walls and 190 buildings have been preserved.
Located on islands off Helsinki, Suomenlinna is a unique historical monument and one of the largest maritime fortresses in the world. Its history is closely entwined with that of Finland and the Baltic region. Helsinki can also thank Suomenlinna for its early growth and prosperity.
Suomenlinna is the only world heritage site in Helsinki. Located on an island just off the shore of Helsinki, it is very easy to reach by ferry. The ferry service is part of the local transit system and if you buy a pass for trains and busses, it will also work on the ferry.
While a great deal of the history of modern Finland can be found on Suomenlinna, it is more than just a museum. Suomenlinna is an actual community with several hundred people living on the island.
I visited in January, which is probably not the best time of year to visit. I’d love to return to Helsinki in the summer and make a return visit when I can spend more time on the island without freezing.