@Quinzy & BadKarma: Not true.
I have it direct from Brad Oliver, the lead programmer at Aspyr on Civ3/4 porting, that there is no Mac editor for C3C. There certainly isn't one on my Civ3 Complete DVD.
The only Mac editor that exists is a port of the vanilla Civ3 version 1.21 editor. It used to be downloadable from MacSoft, was never updated for any later Cv3 version, and doesn't work ever so well on current versions of Mac OS X.