Kastelholm Castle (Swedish: Kastelholms slott) is a Swedish-built medieval castle located off Road 2[2] in Sund, Åland, Finland, approximately 25 km (16 mi) northeast of Mariehamn, overlooking a fjord to the south of the village of Kastelholm.[3][4][5] Along with Hämeenlinna, Olavinlinna in Savonlinna, Raasepori, and Turku, Kastelholm is one of only five surviving Finnish medieval fortresses that are also considered to be architecturally substantial.[6] Built in the 14th century, and held in fief during the Middle Ages by various nobles,[7] feudal chiefs, and kings,[8] it had significant period in the 15th and 16th centuries.