Svartholma was built as a fortress on the new eastern border

In the 18th century, the Russo-Swedish War (1741-1743) ended in peace with the Treaty of Åbo in 1743. Due to the terms of this treaty, Sweden lost territories on its eastern border, and those fortifications which formerly protected the border of south-eastern Finland now remained on the Russian side.

Due to the fear of renewed military hostilities, there was a pressing need for defensive fortifications. Therefore, at the Swedish Parliament of 1747, it was decided to build Suomenlinna Fortress off Helsinki. The Svartholm Sea Fortress,  also known as “The Little Suomenlinna” was made the eastern border stronghold of Suomenlinna.

Svartholma Fortress was built on an island at the mouth of Loviisanlahti Bay, about ten kilometres from the centre of Loviisa Town. Construction began in 1748 based on a design by Augustin Ehrensvärd. The main fortress was completed in 1764. Other parts of the fortress, as well as additional buildings and defences were added after the main fortress was completed.

The fort was built as a symmetrical bastion fortress consisting of tripled defensive fortifications. These were stepped so that the fortress artillery could fire over the beach defences. The front defensive works in turn protected the rear armaments from direct gunfire. The fort was used as a base for the Swedish Navy during the Russo-Swedish War (1788-1790).

Blueprint drawings of the fortress.

The fortress is handed over to the Russians

The Finnish war (1808-1809) between Sweden and Russia was fateful for the Svartholma Fortress. At the outbreak of the war, some of the defensive structures were still unfinished and the fort had only one third of the required complement of weapons.

Russian forces peacefully besieged Svartholma for two weeks until the fortress surrendered on the18th of March 1808 and was taken over by the Russians. Afterward, the fortress lost its importance as a defensive position, becoming a  military base for Russian soldiers, as well as a prison. The prison was moved to Suomenlinna at the beginning of 1847. Later, under the looming threat of the Crimean War (1854-1856), the last prisoners were also transferred to the Suomenlinna Fortress. 

Due to the threat of war, the Russians planned to repair Svartholma Fortress. However, due to a lack of armaments and a weakened defence position, it was decided to empty the fort before the war and to relocate the garrison. When the British navy landed on Svartholma in July 1855, the fortress was empty. The British decided to destroy the rest of the defensive fortifications and the fort was blown up.

Svartholma Fortress seen from the northwest. A watercolour from 1811 by Sergeyev Gavril.

The ruined fortress was renovated for tourism

After its destruction, the locals retrieved the collapsed fortress rock and stone from the island to use as building materials for the town of Loviisa. The existence of the fortress gradually faded into oblivion. The remaining parts of the walls were left to crumble. Over the years, the ruined fortress became covered with vegetation and the island was used as pastureland.

The ruined fortifications began to attract attention in the early 20th century and the first demolition work was begun by the city of Loviisa in 1937. Extensive renovation work was carried out under the direction of the National Board of Antiquities in the 1960s. The walls were cleared of vegetation and restored. In the 1990s, renovation work was extended to the entire fortress area. The restoration of the walls and the upgrading of the island have continued since then in co-operation with the city of Loviisa.

The stepped outer defences of the fortress.

Today Svartholma is a popular tourist destination

Svartholm Island is easily accessible by ferry. You can spend an entire day on this fortress Island, exploring its long and diverse history as part of Finland’s defence system.

Today, this site is a  beautifully restored historic unit with a martial atmosphere that can be felt in the old walls and gun ports. The island offers a variety of activities and guided tours, as well as adventure opportunities for children. There is an exhibition inside the fortress, which includes, among other things, artifacts from archaeological excavations which date from when the fortress was in use.

There are also many other cultural heritage sites around Svartholma. For example, the fortress cemetery is located on the nearby island of Hautasaari (Swe. Begravningsholmen), as well as the former gunpowder cellars on the island of Ruutikellarisaari (Swe. Krutkällarholmen). In addition, sunken shipwrecks can also be found in the area. These sites can be viewed in the cultural environment the cultural environment service window. (in finnish)

Read more about the Svartholma webpage on the! 

Why and how is this location protected?

Svartholma Fortress was an important part of the Swedish defence chain in the 18th century. The Finnish Heritage Agency has defined Svartholma Fortress as a nationally significant built cultural environment.

The whole island is protected in its entirety as a fixed ancient monument by the Antiquities Act. Learn more about the island’s protection! (in finnish)


In summer, the fortress is easily accessible by ferry boat, which departs from the Laivasilta area of Loviisa. The island can also be reached by private boat and there are free berths for guest boats.

View the timetables on Visit Loviisa webpage.

Finnish Heritage Agency’s mapservice

N: 6693363, E: 461575 (ETRS-TM35FIN)