The Town Fortification can be visited
Bernau Town Fortification

The Bernau city fortifications near Berlin are a well-preserved example of medieval defensive architecture.
History+
The origins of the Bernau city fortifications date back to the Middle Ages. A large part of the original fieldstone city wall has been preserved to this day. This wall reached a height of up to eight meters and extended over a length of approximately 1.3 kilometers, originally measuring 1.5 kilometers. The fortification system was supplemented by a system of triple ramparts and moats. The city wall once integrated 42 watch houses (defensive towers), two round towers, and three city gates.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: https://de.wikipedia.org/wiki/Datei:Bernau_bei_Berlin_Steintor_und_Hungerturm.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: 52.6786, 13.5880