AZ-
I obtained a copy of both RRT and Colonization from the same benevolent abandonware site, hence my cognitive correlation between the two. As I recall, this particular collection had been forced from its old server, which barred all of the download links siting a "violation of the terms of service provided", moved, ran out of bandwidth and crashed, and now is slowly dying. Better grab all of the neat titles while you can.
Using Alta-Vista, enter +"GAO Games" in the search field and it will be the foremost link. PC and Amiga (sorry Mac owners) titles you can grab:
Civ I for DOS (be warned: the intro theme, or "STORY.TXT", has been modified to include racial slurs)
WinCiv (cheap, in my opinion)
Pirates! and Pirates! Gold
Railroad Tycoon
A-TRAIN (don't bother downloading - no delay added)
Dune II
-and more, however the links are becoming increasingly broken.
The TTG Guy used to own a site with several of these downloadable commercial classics (and in-depth info on each of them).