The Glehn Castle or manor was established by Nikolai von Glehn on the northern part of the lands of his Jälgimäe Manor to become his new residence. The castle was completed in 1886 and was designed by himself. The castle is surrounded by a park with several buildings like palm house (1900–1910), observatory tower (1910) and sculptures Kalevipoeg (1908), Crocodile (1908), all of those designed by Glehn himself.
After Glehn emigrated to Germany in 1918 the castle was looted and fell into decline. In the 1960s, restoration of the building commenced. The renovated palace was inaugurated on the 24 March 1977.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.