Oldenburg Castle stands at the southern edge of the old centre, a yellow former residence of the counts, dukes, and grand dukes of Oldenburg. Its rooms now form part of the Landesmuseum für Kunst und Kulturgeschichte, with paintings, decorative arts, and courtly interiors that explain why this modest-looking city once mattered politically.
The castle is most useful as an anchor for a walk: the market square and St Lamberti are just north, while the Schlossgarten begins almost behind it.