The Castle can be visited
Hagen Manor

In Probsteierhagen, Schleswig-Holstein, Gutshaus Hagen is a 17th-century manor house that now serves as a cultural and event center. After renovation, it has been accessible to visitors since 2011.
History+
The first mention of the Hagen site dates back to 1264, when it served as a comital hunting ground. In the 16th century, an aristocratic estate economy was established here. The current manor house was built between 1647 and 1649 on the occasion of the wedding of Lucia von Pogwisch and Hinrich von Blome, transferring the estate into the possession of the Blome family. It remained a family seat until it was transferred to a family foundation in 1814.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: http://schloesserrundschau.de/schleswig/schloesser/ploen32.html
This description draws on the facts documented in the linked Wikipedia article; Wikipedia content is licensed under CC BY-SA 4.0. Wording and editing: Mobile History.
Location: 54.3599, 10.2849