Isenburg Castle was built by the Counts of Isenburg around 1100 if not prior. Occupied by several branches of the Isenburg family, it was inhabited into the early 17th century. Shortly after being abandoned, it became a ruin. After the branch of Lower Isenburg had extinguished in 1664 with count Ernst of Isenburg-Grenzau, the county was partitioned between the counts of Walderdorff and the counts of Wied-Neuwied. The present owner of the castle is Maximilian, 9th Prince of Wied, son of Carl, 8th Prince of Wied and Princess Isabelle of Isenburg.
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.