Knock Castle is a four-storey ruin, dating from approximately 1600. The external walls of the castle survive intact, although the tower is roofless. The inside of the tower is entirely ruined, but the remains of a vaulted basement, used as a kitchen, and a spiral turnpike staircase can still be seen. An unusual feature at Knock are the defensive shot holes for pistols, of which three are located under each of the numerous windows.
A short distance to the west is a motte, or mound, with the possible foundations of a 12th-century timber stronghold, known as the Old Castle Knock. Belonging to the Earls of Mar, this structure was destroyed in 1590 by the Clan Chattan (Macintosh). What little remains of the site appears to have evidence of a corn-drying kiln within.
Knock Castle was granted to the Gordons of Abergeldie by the 4th Earl of Huntly, after the battle of Corrichie. Fought on the 28 October 1562, the Gordons were defeated by the forces of Mary, Queen of Scots, during her suppression of the rebellious Huntly.
A feud between the neighbouring clan, the Forbes, intensified when Henry Gordon, the 2nd Laird of Knock, was murdered during a raid by the Forbes and Clan Chattan men in 1592. His brother Alexander Gordon succeeded Henry, and may have built or remodelled Knock Castle.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.