Santa Clara Monastery was founded by Don Sancho Sanchez de Velasco and his wife Doña Sancha García in 1313. Throughout the centuries almost all members of the Velasco family were buried there.
The Gothic church has a single nave and is divided into side chapels. The High Altar has three altarpieces bathed in gold in the Rococo style.
The museum shows the works of art and relics of the monastery, most donated by the family Fernandez de Velasco.
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.