Gardyne Castle was built by the Gardyne family, and an inscribed stone records the date 1568. The date stone also bears the arms of King James VI and the motto 'God save the King'. Together with the distinctive style of some of the architectural features, such as the conical-roofed bartizans, this suggests an attempt to link the building with Royal Stewart architecture, and with the new king, as opposed to his predecessor the deposed Mary, Queen of Scots.
The Gardynes held a long-running feud with the Guthries of nearby Guthrie Castle, leading the Crown to confiscate the lands of both families in 1632. The Gardynes subsequently moved to a nearby residence, and Gardyne Castle became the property of the Lyell family of Dysart.
A large extension was added in 1740, which forms the central part of the current building. A further addition was made in 1910 when Harold Tarbolton was the architect. The building was renovated in the early 21st century.
The castle was remodelled and modernised (adding electricity) in 1910 by the Edinburgh architect Harold Tarbolton.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.