The Great dolmen of Dwasieden was excavated in 1970 by Ewald Schuldt. The megalithic site of the Funnelbeaker culture was constructed between 3500 and 2800 B.C. Of the 54 kerb stones - including the four guardian stones - 41 have survived. The rectangular, roughly east-west oriented chamber at the wide end of the frame, with its western entrance and porch consists of seven supporting stones, a half stone the height of the uprights and five slabs, on which there are three large (on the chamber) and three small capstones. Only the central capstone of the chamber is missing. One of the four guardian stones at the southwest end, which had already been overturned in the past, has 40 cup marks, one of the kerb stones has three more. The site is a prime example of the porch dolmen, typical of this region. A two-metre-long porch runs past the support-high half stone to the 4.0 metre long, 1.7 metre wide and 1.4 metre high chamber. The hall consists of red sandstone slabs, annealed flint and a clay floor.
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.