Civilization IV is a 2005 turn-based strategy game developed by Firaxis for PC and Macintosh, and is the tenth entry in Sid Meier's popular strategy series.MobyGames: Civilization Series Listing

One of Civilization IV's most prominent gameplay additions is the religion system. There are seven different creeds in the game, each of which are tied to a specific technology. Promoting the religion of your choice will higher your culture rating, and will eventually allow you to create a special building tied to that religion. While this feature is not crucial to winning battles in the game, it adds depth the gameplay and is a way to spread your influence to neighboring civilizations.GameSpot: Civilization IV Review (October 26, 2005) One other significant addition to Civilization IV was the graphics, which feature a full 3D world with higher quality unit animations.MobyGames: Civilization IV Entry