Albrechtsberg Castle was probably built in the 12th century and was documented first time in 1230. It belonged to Protestant Neidegger family from 1377 until 1527 and was badly damaged in Hussite Wars. Knight Erasmus von Peuckham converted it into a Renaissance style residence in the 16th century. The castle was again damaged during the Thirty Years' War.
The towering, irregular structure largely dates from the second half of the 16th century. It is characterized by its high, crenellated ring wall, which features prominent watch and defense towers with numerous keyhole slits. The three-story, multi-winged complex includes three courtyards, a southern entrance through a round-arched portal marked '1675' in the gable field, and a main gate in the northeast with a machicolation. One courtyard contains a cross-vaulted arcade on squat columns. Additional features include a smoke kitchen with a pyramid chimney, cross-vaulted rooms, a wooden ceiling marked '1604,' and an 18th-century granary with a hipped roof. The castle chapel houses the burial site of the Neidegger family.
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.