The manor of Ahja was first mentioned in 1553. The current two-storey, Baroque style main building was erected in 1749 by Guillemot de Villebois. Later, the manor belonged to the von Lipharts, von Löwis of Menars and von Brasches. In 1929-97, the building housed a local school. About a kilometre from the manor's centre is a chapel (with a beautiful Neo-Renaissance portal) and family graveyard of the von Brasche's family.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.