The first Trizec-constructed project was THE SHOPPING PROMENADE. It consisted of two fully-enclosed shopping concourses beneath Montreal's 617-foot-high PLACE VILLE MARIE ["Plahs-Veel-Muh-ree"] office tower. 

Dedicated in September 1962, PLACE VILLE MARIE was the first segment of Montreal's present-day UNDERGROUND CITY. Consisting of 1,600 stores and services, and extending for a total of 20 miles, it is the largest subterranean retail complex in the world.

Photo from Wikipedia / "Montrealais"