Once the seat of the dukes of Schleswig-Holstein, this 16C-18C castle now houses two museums devoted to the history of Schleswig-Holstein: the regional museum of Schleswig-Holstein with its extensive arts and crafts collections (earthenware and porcelain), and the regional museum of Archaeology (from Neolithic times to the Vikings). The Renaissance chapel is another highlight of the visit. An adjacent building houses Rolf Horn's fine collection of works spanning from Expriessionism to the present day.