The Bernina railway is a world heritage railway in Switzerland. It is served by the Bernina Express, a touristic train. However, the same track is also served by normal Swiss regional trains. In my opinion, it is much better to take these regional trains instead:
The windows in the Bernina Express cannot be opened. Result: you cannot take pictures without reflections. The regional trains, in contrast, have special photo wagons where the windows can be opened.
The regional trains often have open wagons (see picture) and it's super fun riding them.
The regional trains allow you to get on and off at leisure — for example to visit St. Moritz.
The regional trains run roughly every hour — while the Bernina Express runs only a few times a day.
The regional trains are cheaper.
The caveats with the regional trains are:
The seats cannot be reserved. You have to be early at the track to get the good places.
There is no guarantee that you'll have the open wagons. Then again, in the worst case, shooting pictures is just like in the Bernina express (just cheaper).
For the details, read on.
The Albula & Bernina Lines
The World Heritage rail line consists of two parts:
The Albula line from Thusis to St. Moritz (shown in blue on the map). This line includes the famous Landwasser Viaduct.
The Bernina line from St. Moritz to Tirano (shown in green). This part has the circular viaduct of Brusio.
The rail line is spectacular:
The Bernina Express
The Bernina Express is a touristic train. It serves both the Albula part and the Bernina part of the rail line, and runs services between Chur and Tirano.
The big problem with the Bernina Express is that its windows cannot be opened, so that you cannot take pictures easily without reflections. A Bernina Express representative confirmed this to me by email.
The regional train
The regional train is the normal Swiss railway train that connects the cities in the region. Surprisingly, the trains are specially prepared for tourists.
On the Albula line, the photo wagons are explicitly marked on the booking Web page, so you can make sure you get a train with this facility. On the Bernina line, the open wagons run only in July and August, and only when the weather is good. That said, we had them in August in bad weather.