With the Federal Fortress Ulm, built between 1842 and 1859, Ulm/Neu-Ulm is a first-rate fortification. Adapted to the topographical conditions, von Prittwitz designed a city wall without a regular ground plan.

With the federal fortress, Ulm became a garrison town, which still has an effect today and was given a green belt along the fortress walls, which encloses almost the entire city center of the two cities. Significant parts of the federal fortress have been preserved and are now used in a variety of ways.

Particularly worth seeing is the city wall on the Neu-Ulm side, which provides a good insight into the conception of the facility along the Glacispark. At the height of the Michelsberg rises the monumental citadel of the entire fortress, the Wilhelmsburg with an area of 24,125 m².