Once the domicile of the Counts of Wertheim the castle (extended during 15th to 17th centuries) is one of the most picturesque ruins in Germany with a deep moat and impressive bulwark. In 1618 the castle was partly destroyed by an explosion; during the Thirty Years' War in 1634 and 1647 it was under heavy fire. Today the castle is owned by the Community of Wertheim growing into a more and more attractive setting for cultural events.References:
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.