The St. Birgit Memorial Church was built probably between years 1502-1505. It is dedicated in memory of St. Birgit who died in Rome in 1373 and was proclaimed as a saint in 1391.
Situated on the bordering area between the historic districts of Satakunta and Häme, the architectural style of the church exhibits certain influences from both of these areas. The shapes of the nave, rich in decoration, are typical of Satakunta, whereas the large, protruding cornerstones are unique to a very few number of churches in Häme.
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.