The first recorded mention of Holligen is in 1257, when it was owned by the Teutonic Knights commandry of Köniz. It is likely that there was a castle here to control the Bümpliz-Köniz road and administer the estates. However, very little is known of this building. The current castle was built around 1500 by the Bernese Schultheiss Wilhelm von Diesbach. It was built in the style of a typical Burgundian castle, with a square donjon of massive stone blocks with four towers at the corners. A residential hall with a staircase tower was added around 1575 for Peter von Graffenried.
A map by Thomas Schöpf from 1577 and a city plan from 1623/24 both show the castle surrounded by a ring wall with several small towers. Between the 1624 plan and 1667, the square castle was expanded with the construction and expansion of the residential hall to the west. In the 18th century the castle was renovated in the Baroque style. The facade and windows were redone in 1765.
Between 1991-1994 the castle was extensively renovated and repaired. Today it is owned by the Turmstiftung Schloss Holligen, a foundation that maintains the castle.
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.