Sherbrooke Street
Of course the central part is more a 'cliff' than a canyon because the row of towers faces McGill University.
But east and west of McGill are some of the most massive streetwalls in Montreal.
Outside downtown...
there are several towers + midrises extending very far east of downtown, but they don't form a real canyon
I think it's like Yonge Street north of downtown Toronto
looking west from St-Denis, July 21, 2008
looking north from above, towards Sherbrooke Est and its row of towers, September 11, 2006
Alright, let's go
Downtown
looking west from Bleury/Parc, March 17, 2010
looking east from MacKay, March 24, 2010 (you can see work being done on the Fine Arts Museum's expansion)
looking west from McGill College, September 8, 2009
looking west from Durocher, April 26, 2009
looking west from Metcalfe, April 4, 2009
looking east from Stanley, September 4, 2008 (the massive streetwall WEST of McGill)
looking west from Parc, September 1, 2009 (the massive streetwall EAST of McGill)
looking west from Aylmer, September 15, 2009
...March 17, 2009
Bonus, with the Hilton Garden Inn (37 storeys, 2009), March 8, 2009