Château de Castries has belonged to the House of Castries since 1465. In 1565, Jacques de Castries undertook the building of a new château. The garden was laid out by André Le Nôtre in 1666. The aqueduct, to water the garden, was built by Pierre-Paul Riquet.
The main house was looted and damaged during the French Revolution of 1789 and was restored in 1828. In 1935, it was bought back by René de La Croix de Castries. In 1985, he donated the house to the Académie française. It is open to the public.
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.