Schloss Oberhausen is a 19th-century neoclassical castle surrounded by a moat and the Kaisergarten park, home to the LUDWIGGALERIE — a municipal art gallery showing rotating exhibitions drawn partly from the extensive Ludwig collection of modern and contemporary art. The Ludwig family's donations underpinned several significant German museums; the Oberhausen branch shows international art of the 20th and 21st centuries alongside pop art, comics art, and photography.
The setting is the best part: the castle sits on an old arm of the Emscher river in a landscaped park, and the combination of castle exterior and contemporary art interior is pleasingly incongruous. The gallery is open Tuesday to Sunday; admission is free on the first Friday of each month.