The remains of the Castle can be visited
Kalbe Castle

The castle ruin of Kalbe, a former moated castle, is located in the Altmarkkreis Salzwedel in Saxony-Anhalt. Situated between two arms of the Milde river, it was once a significant Saxon border fortress.
History+
The origins of Kalbe Castle date back to the 10th century, when it was likely built as a Saxon border fortress on the site of a Slavic hillfort. The complex was extensively protected by three moats and four outer bailey, but suffered repeated destruction due to wars and fires. The Marchian noble family of Kalben, which gave the castle its name, was first documented in 1207.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: http://commons.wikimedia.org/wiki/File:Kalbe_Burg.jpg
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: 52.6540, 11.3964