The remains of the Citadel can be visited
Citadel Ludgerusburg

In Coesfeld, North Rhine-Westphalia, the star-shaped citadel Ludgerusburg was built in the second half of the 17th century. It served as the princely residence of Christoph Bernhard von Galen and was named after Saint Ludgerus.
History+
After the Thirty Years' War and the occupation of Coesfeld by Hessian troops until 1652, Prince-Bishop Christoph Bernhard von Galen intended to develop Coesfeld into his residential city. From 1655, the Ludgerusburg was built in the north of the city, complementing the already strengthened fortifications. The citadel had a square layout with four bastions, each bearing a cavalier, and was surrounded by a moat. A lower wall, the Fausse-Braie, protected the curtain walls and flanks. Ravelins and demi-lunes were located in the moat to protect the blind spots. The necessary lands were expropriated and citizens compensated.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: http://de.wikipedia.org/wiki/Datei:Coesfeld_Ludgerusburgruine_2.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: 51.9499, 7.1715