The remains of the fortress can be visited
Fortress Magdeburg-Kavalier VI
Kavalier VI is a well-preserved relic of the Fortress Magdeburg. As part of this defensive system, which from the early 18th century until 1912 was among Prussia's strongest, military architecture.
History+
The origins of Magdeburg's fortifications date back to the 13th century. With the advent of firearms in the 15th and 16th centuries, the city walls underwent extensive renovation and expansion, including a second wall, a moat, and the fortification of the Elbe front. These strengthened structures proved effective during sieges in 1550/51 and 1629. During the Thirty Years' War, the fortress was further expanded under Swedish command, but a neglected southern front led to the city's capture by imperial troops in 1631 and the demolition of the fortifications. After the war, Elector Frederick William ordered the reconstruction in 1666, which took place in several phases and included the construction of bastions and a citadel.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: http://commons.wikimedia.org/wiki/File:Magdeburg_Kavalier_6.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: 52.1299, 11.6228