Fort de la Conchée is an island fortification constructed by Sebastien Vauban. In 1689 Vauban conducted an inspections of French coastal fortifications for King Louis XIV, who wished to strengthen and improve the country's defences. In 1693 whilst the fort was being constructed the English raided the town. They landed on Conchée where they slighted the works and captured those working on the fort.
Again in 1695 the English, with their Dutch allies, attacked the fortress. Though the fort was unfinished, ten guns had been installed, which permitted the French to repulse the attack. The battery then turned its guns on the main attacking fleet causing much damage to it. The fort was finally finished in 1705. The fortress was demilitarised in 1901.
During the Second World war the Germans used the abandoned fort for target practice. The Allies then attacked the fort during St Malo's liberation.
The fort covers almost the entire island. The fortress consists of a granite two-storey structure, with an upper terrace for the fort's armament.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.