The greystone church in Parainen was built in the 15th century (probably in 1440-1460) and is dedicated to St. Simon. The western part of the Agricola-chapel is the eldest component of the church, today a museum. On the churchyard is located the chapel of bishop Tengström, Finland's first archbishop (erected in 1819). The interior of the church is covered with several coat of arms. The rarest one is dedicated to pope Innocentius III.
National Board of Antiquities has named the church and the surrounding Vanha Malmi old town as national built heritage.
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.