Starting this thread to have a place to discuss tourist train rides in CO, of which there are many. I'll start with my favorite one.
Sep 1995. Union Pacific RR steam trip from Denver to Portland, a 2-week trip put on by the Rocky Mountain RR Club and UP Steam Program. We took the first week of the trip, from Denver to Boise, ID.
The trip was marvelous, not a single problem the entire time. The Armour Yellow car fleet of the UPRR is in stunning good shape. The trip gave people a taste of how great rail travel was back in the glory years when fabulous name-trains polished the rails from coast to coast. I've about 400 slides of this trip, I'll post a few of them here.
It was our first trip to CO. We had no idea that the eastern third of the state was prairie. On the way north out of Denver, we saw Bison grazing on the plains, what an amazing sight to an eastern city boy.

One lucky fan got a cab ride over Sherman Hill, with Steve Lee at the throttle.

Engineer and Conductor for the trip. Best jobs in the world.

Crossing the Continetal Divide. The small sign says Creston. Tele-shot taken at a "run-by." The sound of this engine was awesome, simply ear splitting. My late father worked on steam loco's for the B&O in Baltimore, he talked about steam to the day he died. Big engines like this were his favorite.

Pit Stop. The loco burns #5 heavy oil, a thick oil. Use of oil eliminates fires along the tracks that used to be started when hot coal cinders flew out the stack. Here we are in Wyoming, filling up the tender with oil.

Jiffy Lube? Here, the crew uses an alemite gun to push lube into the bearings for the rods. Poor lubrication can burn up the bearings, leading to all sorts of trouble and downtime.

Another run-by on a great day.
For more info on the UP Steam Program, see:
Union Pacific Steam Locomotive Shop