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 have to say, of all the mods I've played of Civ IV, this one truly surprised me. Sure, there have been Rome scenarios, but fleshing out the era into a full-size Civ game... an impressive feat, indeed. It reminds me of the Sengoku scenario in Civ III Conquests for all the right reasons. Full length, no major Civ components missing, and better still, and unlike Sengoku, actually allows random map. Basically everything I look for in a Civ overhaul.
"A designer knows he has achieved perfection, not when there is nothing left to add, but when there is nothing left to take away."
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.