It was probably the American Orient Express, a dedicated, definate crusie or escorted tour train. It offers a series of entirely different itineraries, making maybe ten or twelve or more trips a year. (just guessing.)
It is powered by Amtrak locomotives, so this can cause confusion. A lot of Amtrak railfans, if they travel around often enough eventually usually get a glimpse of the AOE sitting in a station or something somewhere or another.
Again, it has many itineraries. For example, there is a route which goes deep into the beautiful mountainous area of Mexico. I would like to do that one day .
It is quite expensive, but virtually everything is included. Sort of like riding Amtrak deluxe bedroom, except that everyone on the whole train is doing the same sort of thing, going the same places, without people getting or and off local stops, etc.
As wonderful as it sounds, I can think of at least one drawback---you are stuck with the same people the whole time, what if you do not necessarily "connect" with any of them? Guess that is a chance you would have to take. Doesn't matter on Amtrak, because there you can be as sociable or otherwise as you wish.