Ruotsinsalmi Sea Fortress

Kotka, Finland

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The Ruotsinsalmi Sea Fortress in Kotka, Finland, was built by Russia between 1790 and 1796 as part of a fortification system to defend St. Petersburg’s northwestern border.

It consists of several forts, strongholds, gun batteries, and underwater barriers positioned on islands near Kotka, including the notable Fort Slava on Kukouri Island and Fort Elizabeth on Varissaari Island. Fort Katarina, located on Kotka Island, was the central fortress equipped with large cannons and served administrative and religious functions. The fortress complex played an important role during the Crimean War but was destroyed in 1855 by the British Navy using explosives. Today, many ruins remain, including the fortress structures and lighthouse foundations, which are protected cultural sites.

The area is accessible to visitors by boat and offers historical exhibitions, memorials, and scenic views of the strait, preserving the memory of this significant 18th-century military fortification.