Krems castle history dates back to the 11th or 12th century. It was built by the Archbishop of Salzburg and mentioned first time in 1248. In the 16th century it was expanded and remodelled in Renaissance style. After 1730 the castle lost its position as administration residence and was left to decay. Today Krems ruins are well preserved. A small museum room opened in May 2015 exhibiting the history of castle.
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.