Unlike most of the submitted designs, which were box-shape and positioned the two requisite halls (one for symphony concerts and one for opera and ballet) one behind the other, Utzon's proposal featured dramatic, curvilinear forms and placed the halls side by side. The incredible thing is that even as the foundation was being poured, no one knew how the shells—or sails as they're commonly called—could or would be constructed. Photo 2 of 14 in Sydney's Surprising Opera House by Miyoko Ohtake

Sydney's Surprising Opera House

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Unlike most of the submitted designs, which were box-shape and positioned the two requisite halls (one for symphony concerts and one for opera and ballet) one behind the other, Utzon's proposal featured dramatic, curvilinear forms and placed the halls side by side. The incredible thing is that even as the foundation was being poured, no one knew how the shells—or sails as they're commonly called—could or would be constructed.