Burgau Castle was originally surrounded by a water trench which gave the name to the village Burg in der Au ('Castle in the Meadow'). The fortification was of great strategic importance against ongoing Turkish and Hungarian invasions from the East across the nearby Lafnitz river. The castle was first mentioned in 1367 as a property of the lords of Puchheim. Then the municipality and the castle were given as a feoff to the house of Neitberg before being handed over to Weikhard von Polheim. Thanks to newly built fortifications commanded by Erhard von Polheim, the invading Turks could be defied in the years 1529 and 1532. In the end, the indebted property of Burgau was given to Mathias von Trauttmannsdorff, who oppressed the local population with high socage fees. In 1704, Eastern Styria was heavily devastated by attacking Kuruz, Hungarians rebelling against the Habsburgs. The mayor saved the village by offering weapons and money to the invaders.
Today the renovated Burgau Castle houses the mayor's office, apartments and a café. The festive hall and the arcaded courtyard are used for indoor and outdoor cultural events and annual exhibitions for Christmas and Easter.
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.