Smart Idea. When it's cold outside, create an indoor mall. Not only indoors but underground. Some areas are free to enter, some you have to pay. Best to ask the information desk for details and map.
Walked around and it was pretty packed. Montreal can get really cold.
Also ate at the food court. Tried the french savory crepes, Korean bbq beef, mediterranean fried fish, and a nutella crepe. All were pretty good!
The place can be like a maze, so best to carry a map. there are some exits that lead you to the outside. it's very exciting!