The remains of the Castle can be visited
Dillenburg Castle (Ruin)

The Dillenburg Ruin, once a castle complex and later a fortress, is situated on a hill in Dillenburg, Hesse. The accessible casemates offer a glimpse into military architecture.
History+
The origins of Dillenburg date back to the 12th century when the Counts of Nassau erected a castle complex here. This initial castle, characterized by a circular curtain wall and a freestanding residential tower, was destroyed around 1325/27 during the Dernbach Feud. In the mid-15th century, the complex was rebuilt and expanded to withstand emerging firearms. An early artillery rondel was constructed between 1458 and 1462. From the second half of the 15th century, Dillenburg developed into the main residence of the Ottonian line of the Counts of Nassau. Faced with political tensions with the Landgraviate of Hesse, Count Wilhelm the Rich began to transform the residence into a fortress from the 1520s onwards.
Source: Wikipedia · Licence: CC BY-SA 4.0
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: 50.7382, 8.2854