Toronto's opera house, which opened in 2006, is a stunner. Designed by architect Jack Diamond of the renowned Toronto firm Diamond and Schmitt, it has a simple exterior, resembling a house of glass. Inside, in the tradition of truly grand opera houses, there are three stages: main, rear, and side. But the masterstroke in the Four Seasons Centre's design is its perfect acoustics. No small feat given that the structure is set on not one but two major thoroughfares, and a subway line rumbles beneath it. This is home to both the Canadian Opera Company and the National Ballet of Canada.