Biburg Abbey was a house of the Benedictines founded in 1132 by Konrad and Arbo von Sittling-Biburg. They were sons of the Blessed Berta of Biburg, who donated their castle to the Bishop of Bamberg for the purpose. The foundation was originally a double monastery for both men and women; the nunnery however burnt down in 1258 and was not re-built.
In 1555 the monastery was dissolved and the premises came into lay hands. In 1589 the Jesuit College of Ingolstadt obtained the buildings, which were taken over in 1781 by the Knights Hospitaller. In 1808 the monastery was secularised and passed into the possession of the Bavarian State.
The abbey church has remained mainly unchanged from its inauguration in 1140.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.