The first Trizec-constructed project was THE SHOPPING PROMENADE, which was 2 fully-enclosed concourses of stores installed beneath Montreal's 617 foot-high PLACE VILLE MARIE skyscraper. 

Officially dedicated in September 1962, PLACE VILLE MARIE was the first segment of Montreal's present-day UNDERGROUND CITY. Consisting of 1,600 boutiques & bistros -and extending for a total of 20 miles- it is now the largest subterranean retail complex in the world.
Photo from Wikipedia / "Montrealais"