The Château du Birkenfels is a ruined castle in the commune of Ottrott. Originally it was built by Burkhard Berger, a vassal of the bishop of Strasbourg, in the 13th century. The castle's position allowed surveillance of the old Roman road running from Mont Sainte-Odile to Champ du Feu and the valley of the Bruche.
The construction is dated to around 1260. The earliest recorded mention is from 1289. The entrance tower to the house and the lower courtyard are from the late 15th or early 16th century.
The castle belonged the Berger family until 1532, then to the Mundolsheim family until the French Revolution. The castle fell into ruins after the Thirty Years' War and was taken over by the town of Obernai, becoming part of the continuous forest between Obernai and Bernardswiller.
The castle is today in a poor state. Remains include the ditch, wall, keep and lower courtyard.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.