The late 15th century Baia Castle was built by the over ancient Roman ruins thought to be the summer residence of Julius Caesar. On the 29th September 1538 the great eruption, with devastating effects for all the Phlegraean Fieldsi, caused serious damage to the Castle of Baia too. The castle was restored and enlarged by the viceroy don Pedro Alvarez de Toledo.
Today, this cliffside Aragonese castle with sea views is home to the Archaeological Museum of Campi Flegrei.
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.