Baltadvaris Castle was a fortified manor house, earlier sometimes classed as a bastion castle. The masonry castle with wooden fortifications was constructed by Swedish in the 16th century, in a bend of the River Siesartis, in order to secure the road from Vilnius to Riga against attacks from Livonia. It used to be the property of the princely Giedraičiai (Giedroyć) family. The neglected castle and fortifications gradually fell into ruins. Today only the foundations remain as well as parts of the walls and of the castle gates, together with several cellars.
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.