Suomenlinna was built to protect Helsinki

As a result of the wars of the early 18th century, the border between Sweden and Russia shifted westwards, and all of the fortresses formerly built by Sweden to protect their eastern border now remained on the Russian side. Thus, in the Swedish Parliament of 1747, it was decided to build a new central fortress off Helsinki.

The construction of this sea fortress began immediately the following year. It was the largest building project of the Swedish state in the 18th century. The fortress was named Sveaborg, which in Finnish became Viapori.

The fortress saw active construction for a period of about 40 years. It was adapted to six islands and the fortress structures conformed to the terrain. Massive granite stone walls were built to protect the inner structures. While no actual military action took place in the 18th century, the fortress served as a base for the Swedish archipelago fleet during the Russo-Swedish War (1788-1790). A shipyard was also established in Viapori, and new warships were built.

Viapori, as seen from Kaivopuisto Park in 1811. Original artwork by Gavril Sergejev.

The fortress was transferred to the Russians at the beginning of the 19th century

In May 1808, during the Finnish War, the Swedish-held fortress surrendered to the Russians after a short siege. Although Finland was an autonomous Grand Duchy, Viapori remained under Russian rule as a military base. The Russians also extended the fortress to include Santahamina Island, King's Island and Vallisaari Island.

A Russian Orthodox garrison church and new military barracks were built inside the fortress. Further, its appearance was enhanced by adding parks and tree-lined lanes. The main Russian construction project in Viapori was the Susisaari Island shipyard.

During the Crimean War, Viapori Fortress was shelled by the British and French Navy over two days in 1855. It caused considerable damage to the fortress, resulting in the replacement and reinforcement of the cannon batteries and earth embankments. Such fortifications were carried out in stages from the 1850s to the 1880s.

Nevertheless, the military significance of the fortress declined in the 19th century. However, during the First World War (1914-1918), Viapori served as part of the so-called Peter the Great's sea fortress, whose task was to protect the Russian capital of St. Petersburg.

An aerial photo of Suomenlinna.

When the fortress was transferred to the Finnish state, it was renamed Suomenlinna

After Finland's independence and following the Civil War of 1918, Viapori was taken over by the state and renamed Suomenlinna. At this time troops from the Finnish Air Force anti-aircraft and artillery were stationed on the island and a Naval Academy was also established. In addition, there was a dockyard and a prison camp.

During World War II, the Suomenlinna fortress participated in Helsinki's air defence, including serving as a base for the Finnish submarine fleet. However, after the Continuation War (1941-1944), only a few army units continued to operate there.

In the mid-1960s the Finnish Defence Forces abandoned the fortress. Suomenlinna was transferred to the Ministry of Education in 1973. Of all the units of the Finnish Armed Forces, only the Naval Academy remained in Suomenlinna and still operates there to this day. Thereafter, the buildings of the Suomenlinna Fortress began to be renovated for tourism and residential use.

The shores of Suomenlinna.

Suomenlinna is one of Finland's most important tourist destinations

Suomenlinna is one of the largest and finest strongholds in Finland, which has preserved many fortifications from different eras. It is a wonderful day-trip destination and can be easily reached by ferry from Helsinki. All around the islands of Suomenlinna you can see stone walls, earth embankments, cannon batteries, and fine barracks buildings.

Up to 300 fortress buildings have been preserved, among others, the buildings of the Russian merchant quarter. The orthodox church inside the fortress was converted into a Lutheran church in 1928, and today its tower houses an air and sea beacon.

The islands and submarine areas of Suomenlinna are rich in archaeological remains. Shipwrecks and other man-made structures can be found underwater. These sites can be viewed in the cultural environment service window. (in finnish)

Diver in an underwater structure.

Suomenlinna is also a nationally valuable landscape area and a central part of maritime Helsinki, which is classified as one of Finland's national landscapes. The importance of the fortress is also illustrated by the fact that it was selected as a unique military architectural monument to be a UNESCO World Heritage Site in 1991. This World Heritage Site area covers seven islands.

Read more from the Suomenlinna official webpages.

Why and how is this location protected?

The fortress has played an important role in the defence of Finland and it is a unique monument to Finnish military history. The defence equipment of Suomenlinna Fortress is classified as an ancient monument and protected by the Antiquities Act.

The National Board of Antiquities has defined the area as a nationally significant built cultural environment.


Suomenlinna can be easily reached by ferry from Helsinki. You can also dock there with your own boat .

More about transport links in Suomenlinna webpage.

Finnish Heritage Agency’s mapservice

N: 6669255, E: 388185 (ETRS-TM35FIN)