Straßburg Castle fas first time mentioned in 1147. It was built by Roman I, the bishop of Gurk. The chapel was built in the late 12th century, consisting of nave, chancel and apse. In the 14th century, the chapel was raised by one floor, and another floor was erected in the 15th century above the choir. The last modification to to the choir took place in 1682.
In the 14th century, the eastern tower was built on the outside of the northern ring wall. There is a medieval kitchen, still preserved. The western tower (Münzturm) was built in the 15th century.
Today Straßburg castle hosts a folkloristic collection exhibiting objects from rural life of past centuries. The exhibition Women’s Artworks of the Werkmann collection shows unique exhibits from the past 200 years with needlework of rural life, nobility and bourgeoisie.
Ängsö Castle was first named as "Engsev" in a royal charter by king Canute I of Sweden (r. 1167-1196), in which he stated that he had inherited the property after his father Eric IX of Sweden. Until 1272, it was owned by the Riseberga Abbey, and then taken over by Gregers Birgersson.
From 1475 until 1710, it was owned by the Sparre family. The current castle was built as a fortress by riksråd Bengt Fadersson Sparre in the 1480s. In 1522, Ängsö Castle was taken after a siege by king Gustav Vasa, since its owner, Fadersson's son Knut Bengtsson, sided with Christian II of Denmark. However, in 1538 it was given by the king to Bengtsson's daughter Hillevi Knutsdotter, who was married to Arvid Trolle.
In 1710, the castle was taken over by Carl Piper and Christina Piper. Ängsö Castle was owned by the Piper family from 1710 until 1971, and is now owned by the Westmanna foundation. The castle building itself was made into a museum in 1959 and was made a listed building in 1965. It is currently opened to visitors during the summers.
The castle is a cubical building in four stores made by stone and bricks. The lower parts is preserved from the middle ages. It was redecorated and expanded in the 1630s. The 4th storey as well as the roof is from the expansion of Carl Hårleman from 1740-41. It gained its current appearance in the 1740s.