Giecz village was once one of the main centres of Polish statehood in the early Middle Ages, alongside Poznań and Gniezno. In the early 9th century, a small keep was built on a mound on a peninsula on the Giecz lake; fortified with a stockade and earthworks. Since 940 it was one of the key strongholds of the early Piast dynasty. In 1038 during a war with Bohemia, the place was seized by Bretislaus I, who sacked the nearby settlement and sold its inhabitants into slavery. The place quickly recovered and by the 13th century was a centre of administration, trade and commerce in the Greater Poland region. At about that time, the settlement received a town charter and became the seat of a castellany. However, in 1331, it was burnt to the ground, never to recover.
After 1945, archaeologists discovered the remnants of a mediaeval pallatium, a pre-Romanesque rotunda, stone walls, a 13th-century palace and several sites of primitive iron-ore working.
Currently, Giecz is the site of ongoing excavations. There are two habitation phases being excavated at the same location. The first is a cemetery dated to the 10-11th century. The second, located just beneath the cemetery, is an earlier settlement. Features of this settlement include open earthen structures, hearths, storage pits, and rich culture layers.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.