The Gate can be visited
Museum
Town Fortification Jülich-Hexenturm Gate

The Hexenturm (Witches' Tower) in Jülich is the last remaining city gate of the medieval city fortifications and serves as a landmark of the city. It now houses a museum of local history.
History+
Built at the beginning of the 14th century, the Hexenturm was originally known as the Rurtor and served as the western access to the city. It bore various names, including "Gefangenenthürn" (Prison Tower), before the current name "Hexenturm" became established in the 18th century. This name stems from its use as a prison for the Duchy of Jülich, although the number of documented witch trials in Jülich was small.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: http://www.wehrbauten.de/thread.php?threadid=570
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: 50.9208, 6.3560