Underwater Cultural Heritage
The theme of the Baltic Sea and underwater cultural heritage is part of Suomenlinna’s content for 2025.
The underwater cultural landscape and cultural heritage are an essential part of the Suomenlinna Sea Fortress. Underwater remains of human activity are called underwater cultural heritage. Underwater cultural heritage refers to everything that humans have caused, built or lost on the seabed. Along with the underwater natural environment, these remains form an underwater cultural landscape.
2025 is a maritime theme year in Suomenlinna, and its slogan is Waves of Balance—Peace from the Sea Fortress. During the theme year, we emphasise the importance of the sea, history and cultural heritage as sources of peace, tranquillity and strength. At the same time, we also pause to reflect on human vulnerability—finding balance and meaning in life.
The sea and its rhythm can help us to find inner peace to serve as a basis for both everyday life and bold actions. Suomenlinna is a unique environment for taking a breather, drawing inspiration and navigating the waves of life.
Through events, exhibitions and workshops, we invite everyone to dive deeper into the dialogue between balance and action. Come and find your peace in the sea fortress!
Underwater Suomenlinna mobile tour
A new mobile tour reveals the underwater history of the Suomenlinna Sea Fortress!
The mobile tour allows you to discover how the sea fortress grew and developed as a hub for warfare, seafaring and shipbuilding. Explore the wrecks of naval vessels, old fairways and underwater structures.
Dive in with your smartphone! The tour is subject to a charge.
Katso tästä vuoden 2025 aiheeseen liittyvät tapahtumat
The Cellar of the Sea – a dive beneath the Baltic Sea’s surface
Underwater cultural heritage of Suomenlinna
The fortress, founded in 1748, and its surrounding waters have accumulated a wealth of traces of human activity. The cold and low-saline Baltic Sea has preserved everything, from household waste to ammunition, from shipwrecks to kicksleds, and from bicycles to massive underwater dam structures.
The waters surrounding Suomenlinna are home to shipwrecks, the oldest of which has been dated to the 17th century. The majority of the ancient relics are wrecks of wooden ships, but there are also several with metal hulls. The fortress has changed owners twice during its history and, as a result, the oral tradition and archive material of the underwater landscape have been lost. Therefore, the archaeological shipwreck material preserved underwater is a valuable gateway to the past.
Submerged in the Tykistölahti bay is the world’s largest underwater log cofferdam, measuring 100 metres wide and 12 metres high. The dam was intended to protect a repair dock basin that the Russian Baltic Fleet was planning for Suomenlinna. After Finland gained independence in 1917, the project was never realised, but the dam remained on the seabed.
Protection of underwater cultural heritage
The Finnish Heritage Agency, in cooperation with the Coast Guard, is responsible for the protection of underwater ancient relics in Finland. The Antiquities Act also protects underwater ancient relics, and old shipwrecks are protected based on age. The Ancient Relics Register maintained by the Finnish Heritage Agency contains information on over 2,000 underwater discoveries, approximately 800 of which are protected ancient relics.
Marine archaeologists study the underwater world and convey information from below the surface. The roots of enquiry into the underwater cultural heritage of Suomenlinna date back to the 1970s, when underwater research was booming. Over the years, the archives of the Finnish Heritage Agency have accumulated a considerable amount of material about a diverse landscape full of traces of human activity.
Below you will find links to interesting online materials: