Ruotsinsalmi sea fortress

Ruotsinsalmi sea fortress (Finnish: Ruotsinsalmen merilinnoitus, Swedish: Svensksund, Russian: Морская крепость Руотсинсальми; both names meaning Swedish Strait) is a fortification system in Kotka, Finland.

It is part of the South-Eastern Finland fortification system built by Russia after Russo-Swedish War of 1788-1790.

Ruotsinsalmi also acted as an outpost of the Kronstadt sea fortress in Saint Petersburg.

Ruotsinsalmi sea fortress is composed of a number of separate forts, redoubts, and artillery batteries.

The main fortress was the Fort Katarina located on the southern part of Kotkansaari island in the present-day Katariina neighbourhood.

Fort Slava in Kukouri island
Ruins of Fort Katarina
Illustration in Finland framstäldt i teckningar edited by Zacharias Topelius and published 1845-1852.