I didn't grow up in Montreal, and I can only remember coming here a few times as a child or even a teenager. I had ridden in the metro once I think, to go to La Ronde. So before actually moving here at 19, I certainly was no expert. Thus, I think it's funny that during my first trip to France at 17, several people mentioned the same thing to me: "Montreal? Isn't it where there is this big underground city where people live and eat and shop and work without ever getting out?" At the time, I didn't really know what to tell them. Could it really be possible? Could it be possible AND I had never even heard of it?
Of course, now, I know what these people meant. I am now back to work downtown after a four-year absence from the area. And my office tower is connected to a Montreal peculiarity called the RÉSO -a 32 km long network of underground tunnels, shopping malls, office buildings, cinemas, metro and railway stations, hotels, universities, residential complexes, restaurants, congress centers, and so on. It covers about 12 square kilometers, and is considered to be the largest underground network in the world (even though compared to most others I've seen around the world our metro is tiny).
About 35% of downtown buildings are connected this way, there are over 150 access points to it, and it is used by about half a million people every day.
You can guess that the harsh winters have played an important role in this big urban project, because yes, it's very convenient when it's crazy cold (or during a snowstorm) to just leave my desk without a coat on and while wearing my dressy shoes, take the escalator to the tunnel, walk a bit and just emerge elsewhere (where I can get lunch, run an errand at the drugstore, do a bit of shopping, etc.) During lunch hour on winter weekdays, you can easily spot which people are part of the network (wearing normal clothes, no wet or crazy hair, etc.) and which people are not (heavy winter gear, red faces, sniffles).
But. Even if they are well-lit, tunnels are tunnels and as much as possible, I try to steer clear of them. It is usually quicker to get where you need to go by actually using the streets, not to mention that the fresh air is much more invigorating. Whether under or on the ground, people are hurried just the same, but I will always prefer the company of non-subterraneans.
As for the lore these French people alluded to with this almost dreamy air to them, about a self-contained fully functional city people never have to leave, well, it's much more legend than truth. Even though it is technically possible for someone to have their apartment, place of work or study, grocery store, gym, hair salon, clinic, bank, etc. all connected through the metro, the actual number of people who are in this situation is probably very low. In 15 years here, I have yet to meet even one of them! Not to mention that winter or no winter, I can't imagine the cabin fever after a while.