Château de Castelnoubel is situated on a promontory overlooking the Mondot valley near Bon-Encontre. The site where the castle stands has been occupied since the 10th or 11th century. Construction of the current castle began in the late 13th century. It belonged to the Marmande family initially, with Arnaud de Marmande being the first known lord. The Durfort family took ownership after the Marmandes, with Arnaud de Durfort receiving jurisdiction rights from Charles le Mauvais, King of Navarre. The Durforts continued to hold Castelnoubel until the late 16th century, when it passed through marriage to the Secondat family.
In the early 18th century, Castelnoubel came into the possession of Louis Pascault de Poléon and remained in the Pascault de Poléon family until the 19th century.Pierre Loubat and later Joseph-Marie-Étienne Giraud, who served as secretary general of the prefecture of Agen, were subsequent owners.The castle eventually became a historic monument in 1966.
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.