I recommend visiting the Underground City to tourists especially if 1) It is cold when you are visiting 2) You tend to over-eat on vacation, like I do, and need some moderate exercise.
The Underground is something like 18 square miles underground--air-conditioned in the warmer months and heated in the colder months.
Shops, shops and more shops. And the biggest, most diverse food court I have ever seen.
Visiting Montreal during the dead of winter, we walked a good portion of it. It's pretty amazing that something like this was built. I can't imagine a city like Chicago having a system like this....our pedway is pretty sad compared to the Underground City and often under construction.
Free health care and the Underground City? Color me impressed!