The Hohensyburg, a castle complex of the Lords of Sieberg, was constructed on the grounds of a former Saxon refuge, which was conquered in 775 by the Franks under Charlemagne. The castle, which was built around 1100 of Ruhr sandstone, was partially destroyed in 1287 by Count Eberhard I. von der Mark. The castle complex was an imperial fief of the von der Mark counts from 1300. This fiefdom was transferred to Brandenburg in 1609, and later to Prussia.
Two keeps, residential quarters (two-chamber system), the wall ring and the walls around the courtyard complex are still recognisable. In the inside of the castle is a war memorial by Fritz Bagdons.References:
The Château Comtal (Count’s Castle) is a medieval castle within the Cité of Carcassonne, the largest city in Europe with its city walls still intact. The Château Comtal has a strong claim to be called a 'Cathar Castle'. When the Catholic Crusader army arrived in 1209 they first attacked Raymond-Roger Trencavel's castrum at Bèziers and then moved on to his main stronghold at Carcassonne.
The castle with rectangular shape is separated from the city by a deep ditch and defended by two barbicans. There are six towers curtain walls.
The castle was restored in 1853 by the architect Eugène Viollet-le-Duc. It was added to the UNESCO list of World Heritage Sites in 1997.