Taavetti fort was built by Russians between years 1773 and 1803 to strategically important crossroads. It was part of the South-Eastern Finland fortification system and meant to defence Russia against possible Swedish attacks. The first phase in 1773-1781 a circle bastion was completed. Inner parts were built in 1791-1796.
Military use of Taavetti ended already in 1803. Fortress was nearly ruined when the renovation started in 1980’s. Nowadays it’s open for visitors and used for summer events.
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.