The Livonian Order erected Grobiņa Castle in 1253 to protect the roads from Livonia to Prussia. It was a square type building and was a three storey high living block in the southern aisle. It also had a gate tower in the middle of the western wall. The castle was built of bricks and crude stone. Once it had arched ceilings. It was a residence for the local viceroy of the Livonian Order from 1399 to 1590. As support base in south Courland it was many times rebuilt and fortified.
In the times of the Duchy of Courland, the castle was destroyed and rebuilt many times. In the sixteenth and seventeenth century sand walls were erected around the castle. They had a bastion in each of the four corners and a stockade. Later the castle was used as a residence for local German landlords. The castle was destroyed in the eighteenth century. Many famous people have visited the castle, for example: Duke Jacob Kettler of Courland, The King of Sweden, Carl XII and the King of Prussia, Friedrich Wilhelm III.
In the 1970s major conservation jobs were made in the castle, so today the castle ruins are in a quite good condition. Most of the walls are still standing in three story height. Today's castle is a major tourist attraction and also a place for local gatherings and concerts.
The ancient Curonian castle hill (Skābāržu kalns) is located only 100 m from the castle. It is supposed to be the famous Seeburg, which is mentioned in Scandinavian sources already in 9th century.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.