The ancient Desenzano castle was originally built around the year 1000. Enlarged at the end of the 15th century, the castle never became a real military fort, but served primarily as a refuge for the population. The plan of the castle is an irregular rectangle, with the tower that stands out at the entrance on the northern side, protecting the drawbridge, which loopholes for the chains are still preserved. The castle is open to the public.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.