Hachenburg Castle, former seat of the Counts of Sayn, was founded about 1180 by Count Heinrich II of Sayn. Building was finished in 1212 under Count Heinrich III, the founder's son, who was also mentioned as the town's and the castle's first owner. The castle church only arose in the late 15th century and underwent several remodellings until the 18th century.
In 13 October 1654, there was a great fire which burned down the inner town and also the castle. Counts Salentin von Manderscheid and Georg Friedrich von Sayn-Hachenburg undertook to build the town anew, and also the castle, although this time as a Baroque structure. The sweeping Baroque castle was built to architect Julius Ludwig Rothweil's plans between 1715 and 1746. It has had many owners over the last century. For a few decades, however, it has been the seat of Deutsche Bundesbank’s training centre and professional college.
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The Gravensteen is a castle in Ghent originating from the Middle Ages. The name means 'castle of the counts' in Dutch. Arnulf I (918–965), Count of Flanders, was the first to fortify this place, building a medieval bastion on this high sand dune, naturally protected by the river Leie and its marshy banks. This bastion consisted of a central wooden building and several surrounding buildings, also in wood.
In the early 11th century, the wooden building was replaced by a stone residence, consisting of three large halls that made up three storeys, connected by a stone stairwell. The monumental stone staircase, the light openings, the fireplaces built into the walls and the latrines were signs of considerable luxury and comfort in those days. There was probably also a tower.