The town of Rastede is about 12km (7,4 miles) north of Oldenburg and houses the magnificent Castle of Rastede. It was the home of Counts and Dukes of Oldenburg and is still lived in by their descendants. It is, therefore, not open to the public. It is in a public park, so you can walk around it.
It began its life as a monastery but was transformed by Christopher, Count of Oldenburg. Anthony Günther, Count of Oldenburg, had large stables built in 1612. The former monastery was demolished in 1643 and replaced by a new hunting lodge, which was used as a summer residence. When Anthony Günther died, Oldenburg fell into Danish hands, but they did not particularly care for the area. For 40 years, it was the home of Princess Sophie Eleonore of Schleswig-Holstein-Sonderburg-Beck, daughter of August Philipp, Duke of Schleswig-Holstein-Sonderburg-Beck and his third wife Marie Sibylle of Nassau-Saarbrücken. It is unclear how she came to live there, though she did write to King Frederick IV of Denmark to thank him for allowing her to live there with a pension. Apparently, the castle was in quite a dilapidated state already, and she often asked for funds for repairs. She requested to be buried in the nearby St.-Ulrichs-Kirche, and she bequeathed 100 thalers to the church. She is now buried in the crypt of the church. Her sarcophagus was reportedly opened by Canadian soldiers looking for treasures in 1945. Sophie Eleanore had her hands folded still, and she was completely mummified.
The Erbprinzenpalais close by was lived in by Duchess Sophia Charlotte of Oldenburg after she divorced Prince Eitel Friedrich of Prussia.
Rastede is lovely for a day out. It has a train station with connections to Oldenburg, and the park is within walking distance of the station.