Älvsborg, also Elfsborg Fortress, is a sea fortress situated on the mouth of the Göta Älv river. It served to protect Sweden's access to the Atlantic Ocean and the nearby settlement of today's Gothenburg and its four predecessors. The fortress was relocated in the 17th century, this New Älvsborg Fortress is still maintained. Of the Old Älvsborg Fortress, only few ruins are visible today in the vicinity of the Carnegie-pier. The new fortress was founded in 1621 by Gustavus Adolphus of Sweden.
In 1643, a settlement in New Sweden, North America, was named Fort Nya Elfsborg, after the Swedish fortress. This settlement was however abandoned in 1655.
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.