The remains of the fortress can be visited
Fortress Magdeburg-Fort XII

Magdeburg-Fort XII was once part of Magdeburg's fortifications. Located in Magdeburg in Saxony-Anhalt, Germany.
History+
The origins of Magdeburg's fortifications date back to the 13th century. Between 1450 and 1550, modernizations were carried out, including the construction of a second city wall and the fortification of the Elbe riverfront. These defenses proved effective during sieges in 1550/51 and 1629. During the Thirty Years' War, the defensive structures were further expanded under Swedish command, but neglect of the southern front led to the city's capture by imperial troops in 1631 and the demolition of the fortress. From 1666, Elector Frederick William ordered the restoration of the facilities, leading to the creation of bastions and a citadel. In the early 18th century, under Prince Leopold I of Anhalt-Dessau, a belt of eleven bastions was created, later supplemented by another eleven bastions, the Turmschanze, and Fort Berge. Magdeburg surrendered to Napoleonic troops in 1806 and became part of the Kingdom of Westphalia, with the fortress being expanded as part of the French Elbe defense line.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: http://commons.wikimedia.org/wiki/File:Magdeburg_Fort_12.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: 52.1087, 11.6530