Over one and a half century the castle was the residence of the counts, then dukes and grand dukes of Oldenburg. Today it is one of the buildings of the local State Museum for Art and Cultural History. The main exposition is the "Cultural heritage in the historic environment", dedicated to the history and culture of Oldenburg from the Middle Ages to the twentieth century. The museum exhibits items of the castle’s original furnishings, the castle model in 1:200 scale, collection of porcelain, private collections donated to the museum: tin toys and a paper theater. The art gallery of the castle houses portraits of local monarchs, engravings, paintings of the German history painter Anselm Feuerbach, nephew of the famous philosopher, as well as works of the founder of the Munich Secession, painter and sculptor Franz von Stuck.