Schloss Wilhelmshohe. Schloss Wilhelmshöhe is a Neoclassical palace located in Bad Wilhelmshöhe, a part of Kassel, Germany. It was built for Landgrave Wilhelm IX of Hesse in the late 18th century. Emperor Wilhelm II made extensive use of it as a summer residence and personal retreat. Today, the palace houses the art gallery Gemäldegalerie Alte Meister, part of Museumslandschaft Hessen Kassel. Since 2013, Schloss Wilhelmshöhe has been part of the UNESCO World Heritage Site Bergpark Wilhelmshöhe. Beginning in the 12th century the site was used as a monastery. Under Philip I, Landgrave of Hesse 1504-1567 it was secularised and used as a castle. This castle was replaced by a new one from 1606 to 1610 by Landgrave Moritz. The current Neoclassical Schloss Wilhelmshöhe was designed by architects Simon Louis du Ry and Heinrich Christoph Jussow from 1786 to 1798 for Landgrave William IX of Hesse. As king of the Kingdom of Westphalia, Jérôme Bonaparte renamed it Napoleonshöhe and appointed his Head Chamberlain Heinrich von Blumenthal as its governor, with instructions to supervise extensive renovations. After the Franco-Prussian War of 1870/71, the Prussian King offered the defeated Emperor Napoleon III accommodation there. From 1899 to 1918, Wilhelmshöhe was the summer residence of the German emperor Kaiser Wilhelm II. In 1918, after the armistice ended World War I, the Oberste Heeresleitung, the High Command of the Germany Army under Paul von Hindenburg was moved here from Spa to organize and lead the withdrawal and demobilization of the German troops. It remained at Wilhelmshöhe until February 1919, when it moved to Kolberg. The middle tract of the castle was mostly destroyed by Allied bombing during World War II. The first reconstruction was made in 1968-1974 by the functionalist architect Paul Friedrich Posenenske. He completely reconstructed the exterior but changed the structure of the interior for its new function as an art museum. From 1994 to 2000 another renovation was made to bring it closer to the original structure. Since 2013, the Bergpark Wilhelmshöhe, which includes the palace has been a World Heritage Site of UNESCO. Today the Wilhelmshöhe Castle Museum houses the antiquities collection, the Gallery of the Old Masters and the Graphic Arts Collection.