I absolutely ADORE taking the train from Montreal to various places in North America, and I 514% have to say that the Ocean View train from Montreal to Halifax is STUNNING! Not only does it offer majestic views, but half the train is actually a sun-roof or is you would like to say a mobile terrarium.
The route begins at Montreal and makes multiple stops until you reach Halifax. It is a 22-hour ride (one way) that acts as a one night one day hotel but instead it takes you along the most beautiful coastal region in North America! It is 514% a train you want to be on.
The train arrives and departs daily at a fair price of around $200. On the Via Rail it is actually described as "the most liberating and relaxing way to travel" which can't be argued since you have continuous view of the maritime. Personally, I rank it as on of the most beautiful train rides in all of Canada regardless of the season (even though my favorite would be fall).
The train takes you through charming Quebec towns that include water-front houses over looking the St. Lawrence River where you can expect to see nature in all its glory and a variety of wildlife such as beavers, deer, and so on.
In addition, as you look out the window for 22 hours straight at the pure beauty, you can expect to see the beauty of New Brunswick, stunning bridges, and of course the Ocean!