In 1834, Crown Prince Friedrich-Wilhelm of Prussia and his brothers acquired the dilapidated ruin. It served as a hunting lodge for the royal family and still contains a rich collection of antique furniture, paintings, and weapons. The paintings and furnishings from the Koeth-Wanscheid Foundation are displayed on the second floor. This collection includes views of the Rhine, portraits of nobility, and furniture from the 18th and 19th centuries belonging to a Rhenish noble family. Since 1918, Burg Sooneck has been state-owned and is used as a museum. It presents itself as a romantic building, terraced and embedded in roses. The rose gardens were created on the former bastion structures of the 17th century. The interiors show how kings used to live away from their court in the 19th century.
Since 2015, a castle blogger has been residing in Burg Sooneck and the Koblenz fortress Ehrenbreitstein from summer to autumn each year. The blog reports on life in the castle, the Middle Rhine Valley, and its people. The project was developed and realized by the Development Agency of Rhineland-Palatinate, the General Directorate of Cultural Heritage, and the Rhein-Zeitung.
