The Château de Lassay is a 15th-century castle in Lassay-les-Châteaux. The first mention of a castrum in Lassay dates back to the 12th century. Owned by Charles de Vendôme at the beginning of the 15th century, the castle was destroyed by French troops as Charles de Vendôme supported the English during the Hundred Years War.
In 1458, the French king Charles VII allowed the son of Charles de Vendôme, Jean II, to rebuild a castle. The new castle was achieved within one year. The barbican was built in 1497-1498.
Since then, the castle has been left mainly intact and the original 15th-century architecture preserved by the different owners of the castle.
The castle is listed as a Monument historique since 1862. It is open for visiting from April to September.
References:Bomarsund fortress and garrison was built in 1832-1854 by Russian Empire to defence Åland Islands against enemies. British and French fleet attacked against it during the Crimean War in 1854. After a week of fighting the British stormed the remaining fort. Anglo-French forces destroyed it totally after battle. In the Treaty of Paris 1856, the entire Åland Islands were demilitarized, which is a status that has been preserved until this day.
Nowadays there are some ruins left and fortress area is open for visitors.