The electors and landgraves of Hesse-Kassel retreated to 200-year-old Schloss Wilhelmshöhe palace for their "summer break". It is now a museum that houses important art and culture collections.

Landgrave William IX commissioned the construction of Schloss Wilhelmshöhe as the centrepiece of his hilltop park. It was originally made up of three separate buildings. Later on, William II, Elector of Hesse had these buildings connected to each other, which accounts for the palace's now uniform and imposing look.

The family of the German Kaiser still used Schloss Wilhelmshöhe as their summer residence until 1918. It was badly damaged in the Second World War and was gradually rebuilt from 1945 onwards. The left wing is now home to the administration offices. The building in the middle houses unique collections such as the Gemäldegalerie Alte Meister, a picture gallery dedicated to works by the Old Masters. The museum in the building's right wing (the so-called Weißenstein wing) is currently being renovated. Ordinarily, the rooms there are furnished as they were in the times of the landgraves.