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

Fort IIa, a component of the former Fortress Magdeburg, was rebuilt in 1892/93. It is located in Magdeburg, Saxony-Anhalt, at an elevation of approximately 72 meters above sea level.
History+
The origins of Magdeburg's fortifications date back to the 13th century. They underwent multiple expansions and modernizations due to the development of firearms. Following its destruction during the Thirty Years' War and its acquisition by Brandenburg-Prussia in the 17th century, a comprehensive reconstruction took place.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: http://de.wikipedia.org/w/index.php?title=Datei:Fort_IIa.jpg&filetimestamp=20061113111354&
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: 52.0941, 11.6016