Johnstone Castle belonged to the Houstouns of Milliken, who acquired the estate of Easter Cochrane in 1773. The original structure was substantially enlarged in 1771 and 1812 by George Houstoun, who had the structure remodelled in a castellated style complete with a turret at the left hand of the front elevation, possibly by the architect James Gillespie Graham.
The most notable features were barrel vaulted rooms in the ground floor. Externally in addition to the battlemented decoration there was a rope-styled string course. Although the castle and policies were considered particularly picturesque, the continued growth of the town of Johnstone reduced its size and the estate had largely disappeared by the start of the 20th century. Much of the house was demolished in 1950, and most of the remainder of the grounds was purchased by the local authority for housing in 1956.
Today all that remains is the central square tower along with a crow-stepped bartizaned section of an older date.
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.