Suomenlinna Sea Fortress is a UNESCO World Heritage Site, to be preserved as an example of the European military architecture of its time. The constructin of on islands off the coast of Helsinki started in the 1748 when Finland was part of the Kingdom of Sweden. The fortress served as a base in the war between Sweden and Russia. In 1809, after the Finish War, Finland became part of Russia and the sea fortress housed a Russian garrison for 108 years until the Finish independence after the Russian Revolution in 1917.