MashGet

Fortress from WikiPedia:

Fortifications are military constructions and buildings designed for defense in warfare and military bases. Humans have constructed defensive works for many thousands of years, in a variety of increasingly complex designs. The term is derived from the Latin fortis ("strong") and facere ("to make").

Many military installations are known as forts, although they are not always fortified. Larger forts may class as fortresses, smaller ones formerly often bore the name of fortalices. The word fortification can also refer to the practice of improving an area's defense with defensive works. City walls are fortifications but not necessarily called fortresses.

The art of setting out a military camp or constructing a fortification traditionally classifies as castrametation, since the time of the Roman legions. The art/science of laying siege to a fortification and of destroying it has the popular name of siegecraft or 'siege warfare' and the formal name of poliorcetics. In some texts this latter term also applies to the art of building a fortification.

Read more on WikiPedia