The Château de Herrebouc is a castle in the commune of Saint-Jean-Poutge. Though an older building, the present look of the castle is the result of a major campaign of construction work at the start of the 17th century. On the ground floor, the 17th century ceiling is partially conserved. The farm buildings date from this period. The pigeon loft is characteristic of the architecture of the time of Henri IV (reigned 1589 to 1610). The wine cellar is probably a later structure.
The mill retains an intact medieval base. Medieval walls are also visible in the buildings of the farm.
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.