Château d'Avezan castle was built, probably in 1230, on the site of an older castle of which nothing remains. It was expanded in the 17th and 18th centuries. The castle was originally in the possession of the viscounts of Lomagne. In the 18th century the castle was passed into the hands of several families who lose interest and left it to decay. The castle has been restored since 1970s.
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.