Frýdlant castle complex consists of the Gothic castle with a high tower and a Renaissance château. There are exhibits, such as of Albrecht von Wallenstein, the Thirty Years' War, and an armoury of 1,000 weapons used for military and hunting. The castle includes the Chapel of Saint Anne, the Knights' Hall, rooms for the count and countess, and a working kitchen.
In the 13th century the castle was held by the Ronovci family until the middle of the century when Častolov of Ronov was forced to return the castle and other properties to King Ottokar II. The first written mention of Frýdlant is from 1278, when Rudolf of Bieberstein, purchased the castle and surrounding land from the king.
Frydlant castle and town went to Emperor Ferdinand I when Christopher, the last of the line of the Birbsteins, died in 1551. The castle went into the Redern family when Bedřich bought it in 1558. Several new villages were established and the production of linen cloth resulted in an economic boom during the initial years of the Redern family. Marco Spazzio di Lancio, an Italian architect hired by the family, expanded the castle in the 16th century.
At the end of the Thirty Years' War, the castle was possessed by the Swedes. They constructed fortified barbicans and strengthened the defensive walls.
In 1800 or 1801, the Clam-Gallas family opened the castle to the public as a museum.
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.