Bernegg Castle was built in the mid to late 13th century for the Freiherr von Calfreisen, though it was probably called Calfreisen Castle until the 15th century. A mention of Otto von Calfreisen in 1231 indicates that the family lived in the area before the castle was built. They may have lived in an earlier castle which was replaced in the mid 13th century or in the village. In 1259 and again in 1286 the Freiherr was mentioned in the castle. After the extinction of the Calfreisen family in the 14th century, the castle was acquired by the Unterwegen family. Hans von Underwegen was mentioned at the castle in 1386, though they may have acquired it earlier. In 1428 it was acquired by the Sprecher family, who changed the name to Bernegg. The castle then vanishes from the historical record until the mid 16th century when it was described as a ruin.
The castle ruin is located on a hill south of Calfreisen village. The palas is a rectangular building about 11 by 13 meters and four stories tall. The walls are 2.4–2 m thick at the base, tapering to 1.8 m on the upper levels. The ground floor probably served as the castle's cellar. The second story has several small arrow slits in the walls. One of the arrow slits on the south wall was expanded into a door way which now serves as the entrance into the castle. The original high entrance on the third story south wall is still intact. The remains of a brick oven can be seen on the fourth story.
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.