City Wall (CTP1)

City Walls is a city improvement in Civilization: Call to Power.
==Effect==
City Walls increase the defensive strength of any military units within the city by 4. They also defend against religious conversion (50% effective) and Slavers (100% effective).
== Great Library entry ==
Civilization has always needed protection from interlopers, human or otherwise. Early settlements utilized their environments to secure their communities. The Anastazi built their homes directly into the face of cliffs for protection. The Aztecs built their capitol in the center of lake, accessible only by narrow causeways. By the first millennium BC, Greek and Roman cities commonly resorted to heavy stone city walls, many of which remain visible today.