Fortress of Mainz

The Fortress of Mainz was a fortressed garrison town between 1620 and 1918. At the end of the Napoleonic Wars, under the term of the 1815 Peace of Paris, the control of Mainz passed to the German Confederation and became part of a chain of strategic fortresses which protected the Confederation. With the dissolution of the Confederation and the Austro-Prussian War, control of the fortress first passed to Prussia, and, after the 1871 Unification of Germany, to the German Empire.

• http://en.wikipedia.org/wiki/Fortress of Mainz