The Castello di Naro was built on top of a hill in the 14th century by the Chiaramonte family. The complex includes walls with battlements, a square tower built by Frederick II of Aragon and the imposing 'mass of the male'. On the east side there are two mullioned Gothic windows that illuminate the great 'Hall of the Prince', which is located on the first floor of the tower. The portal is flanked by two rectangular bastions. The massive outer walls are interspersed with two cylindrical towers and two square towers.
Inside the walls there is a large courtyard, which housed the accommodation of the garrison, the chapel and the stables, and in the case of attack offered refuge to local farmers.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.