The Ancient Mediterranean MOD features a complete modification of Civilization IV. The game now only takes place in the times of Egypt, Rome, and Carthage. It is a complete overhaul of Civilization IV that leaves the basic mechanics of Civilization IV intact.
I love the mod so far, but wish there were some random villages. I play all of my games on Marathon to get the most enjoyment, but that means the first hour is just me hitting Return over and over again. All in all, it is a great addition to any Civ IV game.