Olavinlinna (St. Olaf's Castle) is a 15th century castle located in Savonlinna, Finland. It is the world's most northern fortress (61°51′N, 28°54′E) .
The fortress was founded in 1475 by a Danish knight, and served to repel russian attacks from the east and to guarantee control of the region for the Swedish Crown.
The castle forms a spectacular stage for the Savonlinna Opera Festival, held annually in the summer since 1912.
Olavinlinna is the initial model for Kropow Castle in the comic book King Ottokar's Sceptre, an album in the series of Adventures of Tintin created by Hergé.
