The Nové Hrady Castle was built in the first half of 13th century. It was damaged in 1573 by a gunpowder explosion and in 1590 by an earthquake. Complete demolition was considered, but only the ruins of the massive bergfried and the adjacent palace were demolished. The rest of the castle complex was repaired and newly fortified according to the design of the Italian architect Antonio Canevallo. The castle lost its function of the aristocratic residence in 1635 and in the following centuries it was used as a library, archive, administration and housing for officials. Today it is owned by the state. Since 2000, it has been open to the public and offers guided tours.
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.