Ahrensbök Charterhouse was a former Carthusian monastery or charterhouse established in 1397. The estates with which it was endowed reached as far as Scharbeutz on the Bay of Lübeck.
During the Reformation the monastery was secularised, and with its estates fell into the hands of John II, Duke of Schleswig-Holstein-Sonderburg, in 1584, who had the buildings demolished.
The building materials were used between 1593 and 1601 for the construction of the castle in Ahrensbök, Schloss Hoppenbrook, which was the principal residence between 1623 and 1636 of the ruler of the newly formed Duchy of Schleswig-Holstein-Sonderburg-Plön while Duke Joachim Ernst I's new castle in Plön was under construction. Once Schloss Plön was finished, the ducal residence was moved there from Ahrensbök, leaving Schloss Hoppenbrook as a secondary residence.
After the death there in 1740 of Duchess Juliane Luise, widow of Joachim Frederick, Duke of Schleswig-Holstein-Sonderburg-Plön, Schloss Hoppenbrook was demolished. The Rathaus of Ahrensbök now stands on its site, in a park in which ditches from the previous castle complex can still be made out.
The only surviving building from the time of the Carthusians is the Brick Gothic St. Mary's church - Marienkirche - which in fact was begun in the first quarter of the 14th century and thus predates the monastery itself: when the charterhouse was established it was taken over for use as the monastery church. It was extended several times, and in 1400 the polygonal quire was added. The tower, with an inscribed sandstone tablet over the portal, was not added until 1761.
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.