Château de Courtanvaux was originally built in the 14th century. It was enlarged and restored in 1450-1490. The Renaissance style appearance was built by Souvré family who owned castle between 1500-1661 and current Neo-gothic style restoration took place in the 19th century. The chateau was owned by three families until 1978.
Today there is 68 hectares of park around the chateau. The park is open to the public and the castle in summer season.
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.