The Fortress can be visited
Federal Fortress Ulm-Fort Prittwitz

Fort Prittwitz is a significant component of the Federal Fortress of Ulm, one of Europe's largest fortress complexes. Located in the north of Ulm in Baden-Württemberg, it bears witness to the impressive military architecture of the 19th century.
History+
The Federal Fortress of Ulm, to which Fort Prittwitz belongs, was constructed between 1842 and 1859. It was one of five federal fortresses financed by the German Confederation after the Napoleonic Wars to ensure the security of its member states. The design and construction management were overseen by the Prussian fortress architect Moritz Karl Ernst von Prittwitz und Gaffron, after whom the fort was later named. Fort Prittwitz itself was built from 1847 to 1854 under the direction of First Lieutenant Arlt and could accommodate a garrison of 413 men. Originally known as Fort Avancé, it was renamed in 1863.
Source: Wikipedia · Licence: CC BY-SA 4.0
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: 48.4205, 9.9812