Slangenburg Castle was constructed in the Late Medieval period. In the 17th century the castle became the property of General Frederik Johan van Baer, also known as General Slangenburg, who rebuilt it for residential purposes.
The last private owners were a German family called Passmann, who are buried in a private cemetery next to the moat. After the World War II all German properties were confiscated by the Dutch government, who thus acquired the castle, which, with the surrounding terrain and the buildings within the outer moat, now forms part of the portfolio of the Rijksgebouwendienst ('Royal Buildings Service'), while the surrounding area falls under the care of the Dutch environmental agency, the Staatsbosbeheer.
At present the castle is used as a guesthouse by the nearby Benedictine monastery, St. Willibrord's Abbey, a newly built structure of the 1950s situated on a part of the castle's former estate. The original monastic community, from Oosterhout Abbey, was initially accommodated in the castle itself in the years immediately following the war.
The estate and the monastery chapel are open to the public. The estate, roughly trapezoid in shape, features a system of lanes which is centuries old.
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.