Gmünd Castle dates from the mid-13th century. During the Austrian-Hungarian War in 1487 it was occupied and destroyed by the troops of King Matthias Corvinus after a seven-years-long siege, and rebuilt from 1502 to 1506 under the Salzburg archbishop Leonhard von Keutschach. During the German Peasants' War of 1525, it was again besieged, though not captured. Archbishop Wolf Dietrich Raitenau had the building enlarged in 1607. Devastated by a fire in 1886, it was restored from 1950 and is today used for theatrical performances, concerts and lectures, including a viewing tower and a restaurant.
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.