The fortress of Ulm was one of five federal fortresses of the German Confederation around the cities of Ulm and Neu-Ulm. With its 9 km polygonal main circumvallation Ulm had the biggest fortress in Germany in the 19th century and it is still one of the biggest in Europe.
After the final defeat of Napoleon in 1815, the victorious powers agreed to defend the states from the inside. The fortresses were one of the few realised projects of the confederation. The fortress Ulm was planned by the Prussian construction manager Moritz Karl Ernst von Prittwitz und Gaffron and built under his supervision between 1842 and 1859.