Situated on the little island, the defensive Sancti Petri fortification was once one of a series of forts that protected the inlet, Caño de Sancti Petri. Of irregular shape and in the Moorish style, it dates from the 13th century. During the 1st century, the Phoenicians settled on the island, founding a temple dedicated to Melqart, their god. When the Romans arrived they dedicated the temple to Hercules.
The castle's watchtower is the oldest building, while the walls and the interior date from the 18th century. The castle was in an advanced state of deterioration, but the authorities of the municipalities of San Fernando and Chiclana de la Frontera funded a major rehabilitation programme.
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.