City Walls (Civ1)

City Walls increase the defense of units inside.
== Civilopedia entry ==
Before the development of large publicly-financed, centralized governments capable of supporting strong national armies, cities were normally left to their own devices for protection. As a result, many civilizations constructed Walls around their cities to protect against invaders from other regions, or from bandits and pirates. City Walls represented a major investment of resources and required many years to complete. But these Walls transformed the city into a fortress, capable of withstanding all but the most determined attack.
es:Muros (I)