The first known owner of Sjöö castle was Peter Laurensson, mentioned in 1409. In 1541 the castle was bought by Jacob Vestgöte Sjöö and named after him. The present castle was built during the ownership of Johan Gabriel Stenbock. The castle was designed by Nicodemus Tessin the Elder and Mathias Spieler. The castle with its park is considered one of the most beautiful castles in Sweden with its perfect and harmonious proportions. In 1813 Sjöö castle was sold to Johan Gustav Baner, and it's still owned by the family Baner.
References:Sigmaringen Castle was first mentioned in the year 1077 in the chronicles of Petershausen monastery. The oldest parts of the castle are concealed beneath the alterations made during the 17th and the 19th centuries. The secret of the earliest settlement built on this defendable rock will never be fully revealed: large-scale excavation work would be necessary, which the extensive land development renders impossible. Judging from the many Roman remains unearthed in the area around Sigmaringen, the 12th century keep known as the 'Roman Tower' could be traced back to a Roman predecessor.
The castle remains that have been preserved (gate, great hall and keep) date back to the Staufer period around 1200. The castle remains were integrated into subsequent buildings. The foundations of the castle buildings are to a large extent identical to the surrounding castle wall.
These remains give us a good idea of how the castle might have looked during the 12th century.