Possibly the thing that most amazes me about this title is the fact that rather than unbalance the original, as expansions are infamous for doing, it levels the playing field. Civilization III is a totally rejuvinated game with Conquests installed. [Jan 2004, p.155]
Think of Civilization III: Conquests as you would an even more densely programmed History Channel. If you found yourself at all invested in the first, you're going to want to check this out. And if the first one intimidated you a little, be afraid. Be very afraid.
Rather than trying to remake the entire game, the team has instead presented us with several "slices" of history (the slice being the basic unit of history) that use the same concepts as the main game but offer plenty of new toys, techs and trials.
Between its entertaining and engaging scenarios, the improvements and enhancements to the regular epic game, and the functional multiplayer, it's the expansion pack that Play the World should have been, and much, much more.