Senftenberg Castle was mentioned first time in 1197. In the 13th century it belonged to the Zebringer family and between the 14th and 15th centuries to the Wallseern family. The castle was destroyed during the rebellion in 1407-1409 and rebuilt later. It was a refuge place during the Siege of Vienna in the Ottoman Wars. The castle was finally destroyed by the Swedish troops in the Thirty Years' War in 1645. Today still impressive ruins with three gates and square keep exist.
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.