The Citadelle of Quebec, also known as La Citadelle, is an active military installation and the secondary official residence of the governor general of Canada. It is atop Cap Diamant, adjoining the Plains of Abraham in Quebec City, Quebec. The citadel forms part of the fortifications of Quebec City, which is one of only two cities in North America still surrounded …The Citadelle of Quebec, also known as La Citadelle, is an active military installation and the secondary official residence of the governor general of Canada. It is atop Cap Diamant, adjoining the Plains of Abraham in Quebec City, Quebec. The citadel forms part of the fortifications of Quebec City, which is one of only two cities in North America still surrounded by fortifications, the other being Campeche, Mexico.