To be privately owned
Hakeburg Castle

On the Seeberg in Kleinmachnow, a municipality south of Berlin, rises Hakeburg Castle, a castle-like country house. It overlooks Lake Machnow and the Bäketal nature reserve.
History+
The origins of the von Hake family in Kleinmachnow date back to the 15th century when they acquired feudal property in Kleinmachnow and Stahnsdorf. The Hakeburg was built from 1906 to 1908 for Dietloff von Hake, a cousin of the then lord of the manor. Architect Bodo von Ebhardt designed the building in the style of a Neo-Romanesque castle. Due to financial difficulties, the estate was sold to the Reichspost in 1936. It was used until 1945 as the residence of Reich Post Minister Wilhelm Ohnesorge and simultaneously as a research and testing center for aircraft and radio technology.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: Jörg Dorowski
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: 52.3989, 13.2194