Reifenstein castle was probably built in the 12th century by the Reifenstein family, a branch of Liechtenstein family. In the 13th and 14th century extensions were completed. 1521, the castle was sold to Sebald Pögl from Thörl and rebuilt in the Renaissance style. 1698 the castle came into the possession of the family Schwarzenberg who still owns Reifenstein lands. The castle was inhabited until 1809. It was damaged during the Napoleon Wars and left to decay.
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.