By Train from Zürich / Zurich (Switzerland) to Andermatt (for Gemsstock and Nätschen) (Switzerland)

These trains, which are operated by SOB and not the national operator SBB, take a slower, but much more scenic route than the alternative express trains between Zurich and Bellinzona.

Those express trains race through the world's longest railway tunnel, which diverts them from the older and most spectacular part of the older Gottardo route.
This older route is more fabulously beautiful than many of the special Swiss mountain railways which are famed for offering incredible journeys.

So if time is on your side, take these trains on a journey from Zurich to Bellinzona and beyond into Ticino.
The usually depart from the street level platforms/tracks in Zurich HB station (gleis 3 - 18) in even hours 
In odd hours, if you want to take the more scenic 'Treno Gottardo' route you can take the trains heading to Milano or Lugano and make a very straightforward connections between trains at Arth-Goldau station.

Final Destination: Bellinzona (from Apr 4th the final destination will be Locarno)

These trains also call at: Goschenen (connect for the MGB trains to Andermatt and beyond)
Airolo; Faido and Biasca

The slower train journey from Zurich to Bellinzona:

The train will spend most of the first 10 mins of its journey travelling in a tunnel, but soon after it emerges into the daylight, the train will ascend upwards from the sure of Lake Zuriich

So from the left of the train (when facing the direction of travel) there are sweeping vistas to be enjoyed down over the lake.

Then, if the weather is behaving itself, after departure from Zug station comes the first highlight of the journey, the view over the Zuger See.
This lake with its mountain peaks on the far shore can be seen on the right for more than 15 mins between Zug and Arth-Goldau stations.

The next beautiful vista to look out for comes after departure from Arth-Goldau station, when on the right, the train passes the Lauerzersee...

Then just to the south of here, also look out on the right for glimpses of the Luzernsee.

After Erstfeld station the express trains enter the world's longest railway tunnel, but these trains take the older Gottardo route.
Between Erstfeld and Goschenen the best of the views are on the left, but it doesn't matter which side of the train you are seated on, in order to enjoy the incredible views over the village of Wassen with its white church on a hilltop.
That's because the railway loops in order to climb the mountain, and as it does so, the village can be seen from both sides of the train.

After departure from Goschenen the train enters the older Gotthard Tunnel, and between that tunnel and Bellinzona there are fabulous views from both sides of the train.

The railway will loop around in order to descend the mountains to the south of Airolo station, but this is a prelude to the final highlight of the trip, which occurs as the train descends the mountain on another set of looping curves between Faido and Biasca.
The views looking down the valley with the railway tracks below are breathtaking!

From Zurich Airport/Flughafen:

There are no direct trains between the station at Zurich Flughafen/Airport and Bellinzona.

You will have to change trains at Zurich HB station.

Making the transfer will be much easier if you take a train from Zurich Flughafen to Zurich HB which uses the same part of Zurich HB station (platforms/tracks/gleis 3 - 18) that the trains on to Bellinzona will depart from.
These include the RE services heading from the airport to Luzern or the locals trains on line S24 heading to Zug.