Northern Italy with the Bernina Express

Rome2Rio shows a train-bus combo through the mountains with several connections that goes back to (or starts from) Pontresina, Switzerland and continues via Merano but it's not ideal. I believe there was a better train-bus-train connection through the mountains a few years back that no longer runs (whether from Varenna on Lake Como or the Swiss towns).

So trains from Tirano along Lake Como to Milan, then the main line train as far as Verona will be much faster. Find on SBB.ch or Trenitalia.com, not on some other schedule sites.

The Bernina line is a local line built literally to keep a chunk of Switzerland together with its motherland, and was not planned as a long range line; while being one of the most scenic lines in the world, using it as an international connection means long detours.
I see only two ways to do the Bernina line and end in Bolzano with trains:
1. Zurich - Chur - Bernina - Tirano - Milano - Verona - Bolzano
2. MIlano - Tirano - Bernina - Chur - Buchs - Feldkirch - Innsbruck - Bolzano

Well, actually there is another one, involving a bus ride in the Swiss National Park. I do not know if I should advice because it may not ride all year long and if you get a connection wrong you may get stranded in nowhere land:
3. Milano - Tirano - Bernina - St.Moritz - Zernez - bus to Mals/Malles - Merano - Bolzano

(there would be still another one, via a bus to Landeck, but we would be getting really exotic).

The 811 bus from Zernez to Mals runs frequently, every 1 or 2 hours. Slight problem is that there is a construction notice on the line until Oct 23.

The postbus service 90.811 between Zernez, staziun and Mals, Bahnhof/Malles, stazione is limited.
The stations Glurns, Tauferer Tor + Glurns, Stadtplatz are not served.
The buses are being rerouted.
Reason: Construction work
Duration of restriction from 05.05.2016 until 23.10.2016 .
The online timetable at www.sbb.ch has not been changed. Please pay attention to the information in this announcement.

Thanks for the great info.I really appreciate the links everyone added!

Now my other question is Tirano worth a couple of days? I have Rick's book but would also like some other thoughts.

It struck me as a small place and I would doubt if it could keep you going for a couple of hours let alone a couple of days.

Maybe there is more to the town than first appearances indicate.

No, maybe Bormio up the same valley but no train service.

I also would not stay in Tirano, having visited it for a few hours last year. Staying in Pontresina puts you really in the mountains or staying in Varenna puts you on Lake Como and one hour away from Milan.

Thank you

Obviously this is somewhat subjective, but to me Bolzano feels like a very large town or smallish city, and it's located in a relatively flat area with just one 'dominant' mountain. I didn't really get the feeling that I was in the Dolomites until we left Bolzano and spent time in Ortesei and the Val Gardena. Although the roads are twisty in the Ortesei area it is otherwise easy driving so you might want to consider renting a car to facilitate experiencing the mountains. Rental car office hours are limited in Bolzano, particularly on weekends, so if you plan to rent a car there you may want to check hours as you are roughing in your itinerary, rather than waiting until you have hotels booked, etc.

Last year, we flew into Zurich in the morning, train from airport into City to do a quick walk about with lunch before taking 3 (I think) train connections on the Bernina line (not the fancy train cars), switching at the Swiss/Italian border and then down the Eastern shore of Lake Como, arriving in Varenna in the evening. We loved Varenna and stayed 2 nights before taking train to Milan. We enjoyed staying in Varenna and would have stayed longer if we knew how beautiful and relaxing the area is.
Then you can take train to Florence to CT and/or Tuscany or head East to the Dolomites and/or Venice.
We enjoyed using the trains and not driving.