Kotka, city, southeastern Finland, on two islands, Hovinsaari and Kotkansaari, at the mouth of the Kymi River on the Gulf of Finland, east-northeast of Helsinki. Kotkansaari was fortified by the Russians between 1790 and 1800, and its main fort was destroyed by a British fleet in 1855 during secondary operations of the Crimean War. Kotka was founded in 1878 and was greatly developed during the late 1930s. A Greek Orthodox church (1795) is the oldest building in the city; there is also a Lutheran church (1898). The Kymenlaakso Museum, 10 mi (16 km) northwest, was originally built for Tsar Alexander III. Connected by rail and road to the mainland, Kotka is a major seaport for eastern Finland and an important industrial centre that specializes in lumber, pulp, cellulose, and phosphate exportation, as well as petroleum importation; the city also has sugar refining and flour milling. Pop. (2000) 53,904.