Suomenlinna, known until 1918 as Viapori, known in Swedish as Sveaborg, is a fortress in Finland. It is located on six islands in the sea near Helsinki.
Construction of the fortress started in 1748 when Finland was still part of the Kingdom of Sweden. Sweden wanted to defend the sea areas against Russia. They also needed a place to fix their military ships. In 1808 Russia ruled Finland. They made the fortress stronger to defend Helsinki, which was now the capital of Finland.