I took a ride on the Boone Scenic Valley Railroad as a kid for a field trip and I enjoyed it throughly. I still remember the train stopping over the terrifyingly high bridge which I now know is the Kate Shelly Bridge. The train path is just as beautiful from the bottom of the valley if you take your own tour around the gravel roads below.
The railroad offers train tours with dinner in-car most weekends throughout the nice months. I would highly recommend them to anybody who has such an opportunity. They also have tours that don't require a steak dinner purchase throughout the afternoons, also in the nice weather months.