Levänluhta is a swampy source known for mysterious prehistoric findings. According archaeological excavations about hundred people have been buried to the former lake of Levänluhta in the Iron Age. Archaeologists have also found several remains of bronze and silver jewelry and tools.
There are remains of buried children, elderly and animals of different ages. The human bones of Levänluhta are dated to the 300-700's. They are historically thought to be sacrificed human victims, but the site can also be an ancient cemetery for people died of starvation or diseases.
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.