Trim Castle, the largest Anglo-Norman castle in Ireland, was constructed over a thirty-year period by Hugh de Lacy and his son Walter. Hugh de Lacy was granted the Liberty of Meath by King Henry II in 1172 in an attempt to curb the expansionist policies of Richard de Clare, (Strongbow). Construction of the massive three storied Keep, the central stronghold of the castle, was begun c. 1176 on the site of an earlier wooden fortress. This massive twenty-sided tower, which is cruciform in shape, was protected by a ditch, curtain wall and moat.
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.