The remains of the castle can be visited
Gänseburg Castle

In Putlitz in the Prignitz region of Brandenburg, lie the remains of the Gänseburg castle ruin. As the former ancestral seat of a noble family, it shaped the development of the surrounding region.
History+
As early as 946, a Slavic castle at this site was documented when King Otto I endowed the Diocese of Havelberg with, among other things, the castle and district of “Pochlustin”. Following the victory over the Wends in 1179, the knight Johannes Gans from the Altmark was enfeoffed with the castle and its surrounding lands. From this time, Putlitz became the ancestral seat of the Gans family.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: Roland Neubert, Halle (Saale)
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: 53.2513, 12.0407