The first documented mention of Burg Reichenstein dates from 1208. Following this, the Burg Reichenstein was attributed to Ludwig III of Reichenstein between 1310 and 1320 for the protection of his territory and possibly as a customs station.
Since the 16th century, it has been considered a ruin and was destroyed in 1618 by its then-owner Count zu Wied when the Count of Sayn intended to acquire it. Since then, the ruin has continued to decay and was in private ownership until the 20th century. In recent years, the ruin has been managed by an association, and extensive restoration work has been carried out, including the establishment of the Walpodenstube, which can accommodate approximately 30 guests.
The castle can be visited at certain times, and festivals and events also take place in and around the castle. In addition to the foundations of the other castle buildings and a partially filled-in well, which was formerly 40 meters deep, the still towering ruins of a four-story residential tower give the ruin its characteristic appearance.
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.