The southern wing of Wilhelmshöhe Palace – the Weissenstein Wing – originally housed the state rooms and private apartments of the Landgravial family and high-ranking guests. As well as the palace of Wilhelmsthal at Calden and Löwenburg Castle, the Weißenstein Wing is one of the Museumslandschaft palace museums. It is the only one among the Kassel palaces to retain its historical furniture, and it has survived WWII largely undamaged.
The builder, Landgrave Wilhelm IX, later Elector Wilhelm I (r. 1785–1821), commissioned his apartments to be decorated in an early Neo-Classicism. Besides the exquisite furniture, it is the bright Round Room in the béletage in particular that presents visitors with a distinct image of this era of interior design. Under King Jérôme of Westphalia (r. 1807–1813) and his successors the interior was completely refashioned in the French Empire style; it was in Jérôme's time that the valuable mahogany furniture was shipped to Hesse from the factories in Paris. The Marble Bathroom with its illusionistically painted walls dates from the time of Elector Wilhelm II (r. 1821–1831), as does a gallery of paintings including works by Johann Heinrich Tischbein the Elder (1722–1789), his disciple Wilhelm Böttner (1752–1805), and outstanding French painters of the 18th century that provides several highlights of the decor.
Today the Weissenstein Wing no longer conveys an authentic insight into courtly living of the time around 1800. It does, however, combine outstanding pieces of palace furniture from the Louis Seize (Empire) and early Neo-Classical periods. While some of them were part of the original furniture of Weissenstein Wing, others were brought in from other Kassel palaces and townhouses that have not survived.