Greifenstein castle overlooks the Danube river. Approximately opposite is Burg Kreuzenstein, on the north shore of the Danube. The castle is thought to be built around the 11th century, and was first mentioned in 1135. However, the owners of the castle changed owners frequently during its service from the 11th century to 1918. It began life playing a significant role in the defense system along the Danube.
More recently, in the 16th century, the castle served primarily as a notorious prison of the ecclesiastical court. Throughout history, the castle was repeatedly invaded and damaged, but repaired, again and again. It was inhabited until about 1770, when it was abandoned and fell into disrepair. Until 1803, it belonged to the Bishops of Passau.
Johann I von Liechtenstein refurbished it in 1807–08 in the Romantic style but at the end of the 19th century, the castle fell again and was sold in 1918, coming into private ownership.
Today The castle has remained in private ownership and is presumed to be on sale.
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.