That’s easy: The Bernina Express.
This is a narrow gauge train operated by a Swiss company, Rhatische Bahn. It runs between Tirano in Northern Italy and Chur in Switzerland. Start to finish, it’s about a four hour, 15 minute trip.
I took this train several years ago and it was an extraordinary experience.
There are lakes, picturesque villages, stone viaducts and incredible mountains. Oh, yes … and glaciers! The rail cars are spotlessly clean, as you would expect from a Swiss train, and it moves at a leisurely pace - just what you want when traveling through scenery like that. (Please note that the rail cars shown in these photos have since been replaced with more modern equipment with larger windows.)
The Glacier Express is probably better known but, for my money, the Bernina Express experience is as good if not better.
If you love train travel and scenery that will take your breath away, this is the ride for you!