Linköping Castle is Sweden's oldest profane building. The oldest part, west wing, dates from the 12th century. Currently the residence of the County Governor of Östergötland, the castle has been home to governors and bishops since the 13th century. The most famous bishop to live in castle was probably Hans Brask, Sweden's last Catholic bishop.
The Linköping Bloodbath, the public execution by beheading of five Swedish nobles in the aftermath of the Battle of Stångebro, in 1600 was held in either in Linköping market square or in the castle courtyard.
In 1700 most of Linköping city burned down, but the cathedral and castle survived. The decayed castle was moved as a city prison. The restoration began In 1796 and then the castle got its classicism style appearance. In 1880 it was again renovated to the neo-Renaissance style, but restored back to the current classicism in 1930s.
The old tower of the museum features an exhibit of the history of the castle, cathedral and diocese from the 12th century to today. Unique 14th century textiles and other valuables - especially from Sweden's empire period - are on display in the treasury. You can see a big model of the castle's state apartments in the great hall.
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.