The remains of the Castle can be visited
Château de Dudelange

On the wooded Mont St. Jean to the west of Dudelange, in southern Luxembourg, lies the Château de Dudelange, a historic castle complex. The ruin is now freely accessible.
History+
The first mention of Dudelange Castle dates back to around 1400. At that time, the complex, owned by the Lords of Gymnich, was destroyed by Robert de Bar. In the early 15th century, reconstruction of the fortification began. At the beginning of the 16th century, the castle underwent a transformation, incorporating Gothic and Renaissance elements.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: http://en.wikipedia.org/wiki/File:GEHAAN1w.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: 49.4904, 6.0599