Cinzano Castle construction began around 1666 when the Marquis Carlo Renato Della Chiesa decided to enlarge and embellish the ancient castle and to surround it with a garden. In the beginning of the 19th century, the branch of the firstborn of the Chiesa family died out and the castle was sold with all of its possessions, which were divided up.
In 1872, the Marquis Ludovico Della Chiesa reacquired the castle and restored it in a Neo-medieval style embellishing it with new crenellation copied from that of the older tower and giving the castle a new rising entrance and a small out-building for the gardener.
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.