The Provincial Museum concentrates on the cultural history of Southern Savo and the sailing history of Lake Saimaa. It is located in a former state granary designed by Ernst B. Lohrmann was completed in 1852.
The permanent exhibition "On the platform, life on the shores of Lake Saimaa" displays the living conditions on the shores of Lake Saimaa. It talks about prehistoric times, Sääminki Church art from the 18th century, a Savo cottage from the 1920s, ship models and Finland’s oldest used Savo-style boat. The museum has also four museum steam ships: steam tug Ahkera (1871), steam schooner Salama (1874), passenger steamer Savonlinna (1904) and tarred steamer Mikko (1914).
First record of Kastelholma (or Kastelholm) castle is from the year 1388 in the contract of Queen Margaret I of Denmark, where a large portion of the inheritance of Bo Jonsson Grip was given to the queen. The heyday of the castle was in the 15th and 16th centuries when it was administrated by Danish and Swedish kings and stewards of the realms. Kastelhoma was expanded and enhanced several times.
In the end of 16th century castle was owned by the previous queen Catherine Jagellon (Stenbock), an enemy of the King of Sweden Eric XIV. King Eric conquered Kastelholma in 1599 and all defending officers were taken to Turku and executed. The castle was damaged under the siege and it took 30 years to renovate it.
In 1634 Åland was joined with the County of Åbo and Björneborg and Kastelholma lost its administrative status.