La Hougue des Geonnais is a passage chamber from the Neolithic age. It is today largely ruined by quarrying prior to the initial excavation in 1929. There is no capstone anymore. At that time the chamber was found to have a paving of pebbles and a large quantity of pottery fragments were disguarded in the spoil heaps. Excavation between 1985 & 1990 revealed a chamber that was probably constructed in two phases. A D shaped chamber being built first and then later extended to its current form. In 1990 some of the main chamber's missing uprights were replaced by dated, modern grantite blocks. A vast number of finds included pottery, flint scrapers, arrowheads and broken querns.
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.