Linn Castle in North Rhine-Westphalia by EuroTourData
Linn Castle is the restored water castle, built around 1250 as the fortified residence of the Lords of Linn.

Image copyright info
© Creative Commons: Krefeld, Linn, Burg, 2014-09 CN-01, author Steffen Schmitz. License: CC BY-SA 4.0. Cropped from original.
Linn Castle history
Linn Castle was built between 1195 and 1250 on the site of a tower house. At the beginning of the 14th century, the fortifications of the castle were expanded. In 1477, during the Cologne Diocesan Feud, the castle was besieged by the Archbishop-Elector of Cologne. Around 1620, the old fortifications were replaced by new ones, much stronger, with five bastions. These fortifications could withstand the siege of the castle by troops of the Hessian and of the Kassel for four weeks, but still, the castle was captured. Between 1643 and 1645 the conquerors expanded and fortified the castle again.
The castle was completely destroyed during the War of the Spanish Succession. The Linn magistrate refused to restore the castle because the castle had lost its military significance and since 1728 the castle was considered uninhabited. Since 1950 the castle has been completely restored. The castle currently houses Museum Burg Linn.
Source
The article Burg Linn of German Wikipedia.