Waléran, the first Count of Arlon, built a fortified chateau at the top of the town during the 11th century. Along with the town ramparts, this was completely destroyed in 1558 when Arlon was pillaged by the troops of the Duc de Guise. When the Capuchin monks arrivedin Arlon in 1621, they built their abbey on the ruins of the castle.
In 1681 a Vauban-type fortified wall was built transforming the abbey into a citadel. After being the victim of alightning strike in 1719, it was decided to dedicate the church to Saint Donat. The old religious foundation of the Capuchins was finally abandoned in 1796 - Only the church survived and was then restored and renovated during the 20th century.
References:Towering 52 meters above the sea, Bengtskär lighthouse is the tallest one in Scandinavia. The building started in in 1905 after the shipwreck of S/S Helsingfors and was completed in 1906. The lighthouse was designed by architect Florentin Granholm. On December a special petrol lantern, designed and built in Paris, was brought to Bengtskär and installed atop the tower.
German fleet bombarded Bengstkär in the First World War in 1914. Since the Gulf of Finland was heavily mined, it was not until 1919 that the surrounding seas were declared safe for shipping, that the light was lit again.
After the war the military value of Bengtskär increased as part of the defence system of independent Finland. In Second World War (1941) Soviet Union made a suprise attack to island. After a bloody battle, the small Finnish garrison emerged victorious. Intermittent repairs to the facility continued during the post-war period.