Toronto could have its own thread about this.. So much was razed over the years.
A number of them were already mentioned on the first page but here are some others.
The Old Toronto Star building is the most obvious one:
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Replaced by First Canadian Place.
The Ford Hotel was a big loss as well:
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Replaced by The Atrium on Bay.
The old General Post office:
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Replaced by
this.
The Beard Building (aka Toronto's first skyscraper):
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Replaced by nothing, now a condo building.
The Toronto Armouries:
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Replaced by York County Court House.
Toronto Registry Building:
.
Replaced by Nathan Phillips Square.
Shea's Hippodrome, considered one of the "Big Four Vaudeville Theatres in North America":
.
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Replaced by New City Hall.