Suomenlinna is the fortified island site built to defend Helsinki and is a UNESCO World Heritage Site in Finland.
Construction began in 1748 when Sweden controlled Finland and wanted to strengthen its position against Russia. The fortress was originally called Sveaborg, meaning “Swedish fortress,” while its Finnish name, Suomenlinna, means “Castle of Finland.”
The defensive complex spreads across several linked islands at the entrance to Helsinki. Its structures include bastions, dry docks, barracks, tunnels, churches, and residential buildings. Suomenlinna changed hands after the Russian conquest of Finland in 1808 and was later used by the Russian Empire.
Finland gained independence in 1917, and the fortress received its Finnish name soon afterward. UNESCO inscribed Suomenlinna in 1991 as an outstanding example of European military architecture of its period. Today it is both a historic monument and a living district reached by ferry from Helsinki.