The St. Olaf's castle is a fifteenth-century building, erected in the town of Savonlinna in Finland. The castle was founded by Erik Tott in 1475 in order to provide safety for the Kingdom of Sweden. The fortress survived numerous sieges during the Swedish-Russian wars, however, it capitulated twice (in consequence of the second capitulation the territory of south-eastern Finland was surrendered to the Russian Empire). The castle, which at present is a tourist attraction, is the furthest northern medieval stronghold, which exists until today.