Montreal’s underground pedestrian network, which began beneath the Central Station complex, took off during the 1960s when Place Ville-Marie was built.
This initial core would expand considerably with the construction of Place Bonaventure. The metro, which opened in 1966, would extend it much farther still.
Here too, the transportation infrastructures criss-cross and complement each other. The elegant Place Bonaventure metro station, for instance, designed by Montreal architect Victor Prus, links the CN complex with the rest of the city and allows pedestrians to reach Windsor Station without venturing outdoors.
More information: http://en.wikipedia.org/wiki/Underground_City,_Montreal