National Historic Sites of Canada.

1.) The Chateau Laurier Hotel, Ottawa 

2.) Kingston Penitentiary, the Prison for Women, Isabel MacNeill Halfway House and Corrections Canada Museum.

3.)  Central Experimental Farm, Ottawa.

4.)  Union Station, Toronto - Politicians David Crombie and John Sewell prevented the demolition of the train station during the 1960's. The Ontario government is trying to preserve historic buildings in the area, the government created "The Union Station Heritage Conservation District" which will protect:
The train station
the John Street Roundhouse
 Royal York Hotel
 Dominion Public Building - One Front Street West 

5.)  Royal Canadian Mint - 320 Sussex Drive, Ottawa- Prime Minister Brian Mulroney saved the Mint: Part of an article by Susan Delacourt, November 1, 2010:
     "Nearly 25 years ago, former prime minister Brian Mulroney was headed to work, sitting in the back of his limousine as it headed down Sussex Drive. As the car passed the Royal Canadian Mint Mulroney gazed out the window and was startled to discover construction workers busy dismantling the magnificent stone architecture at the 1908 building. "Stop the car" Mulroney told his driver.The prime minister got out and asked the workers just what they thought they were doing. The men explained they had been sent by Public Works. Mulroney bluntly gave them a new work order. "You can put your tools down, guys, because you're not doing it." The prime minister then called the Minister of Public Works and told him to halt the deconstruction."

6.)   Postal Station K, 2384 Yonge Street, Toronto - The former Montgomery's Tavern, where William Lyon Mackenzie organized the Upper Canada Rebellion. 

7.)  The Dominion Astronomical Observatory, Carling Avenue, Ottawa - The main observatory and surrounding buildings are part of the Central Experimental Farm National Historical Site of Canada. During the year 1965 my schoolmates and I visited the Farm during a field trip; we all had a chance to use the Dominion Observatory telescope. The telescope was removed from the building, and the government wanted to demolish the site because of budget cuts. 

The Dominion Observatory, Ottawa, Ontario. (Photo from  Wikipedia.)

8.)  Rideau Hall and Landscaped Grounds, 1 Sussex Drive, Ottawa - The Right Hon. Jeanne Sauve, Governor General of Canada, banned the public from the grounds of Rideau Hall during the year 1986. However, the Right Hon. Ray Hnatyshyn reopened the gates when he became Governor General of Canada in 1990.