The Castle can be visited
Neue Kammern Castle

The New Chambers in Potsdam was built between 1771 and 1775 for Frederick the Great. Located in Sanssouci Park, directly west of Sanssouci Palace, it is distinguished by its interior design in the late Frederician Rococo style.
History+
The building now known as the New Chambers originally served a different purpose: from 1745, it was an orangery designed by Georg Wenzeslaus von Knobelsdorff, where the potted plants from the palace terraces overwintered. Between 1771 and 1775, it was converted into a guesthouse under the direction of Georg Christian Unger. The exterior dimensions and the floor-to-ceiling French windows were retained, while the interior was transformed to include seven guest quarters and two ballrooms. A notable addition was a dome placed on the central section, creating architectural symmetry with the Picture Gallery building to the east.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: Joachim Schneeleopard
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: 52.4036, 13.0356