Waldeck Castle was first mentioned in 1124. It was owned by the Landgraves of Leuchtenberg, who sold the castle in 1283 to Duke Ludwig of Bavaria. In the Spanish War of Succession, the castle was besieged by imperial troops , taken in October 1704 and demolished by order of Emperor Joseph I. Although the castle was rebuilt, it was burned down in 1794 and since then has been ruined. Since 1982, the ruins have been excavated and restored.
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.