Château du Bousquet was built in the 14th century. Today it hosts a museum of ancient art from the Middle Ages to the present day. The castle has very well-preserved sample of late medieval architecture (furnished interior, furniture, objects, paintings).
The castle, which belonged for four centuries to the Roquefeuil-Blanquefort family, comprises six towers (two hexagonal in the middle of the two front and rear facades, four rounds at each corner). The central tower of the south facade, which contains the staircase is pierced on the ground floor of a radiating Gothic door. The typically feudal and defensive character of the castle is somewhat mitigated by the existence of later windows on the three floors. The defensive system which surrounded it (enclosure, ditch, fortifications) disappeared, replaced by two wings in the 17th century. Inside, the ground floor has kept its kitchen intact, with the mesh stage where the musicians were based. The chapel retains a decoration painted by Debert in 1709.
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.