The design was nearly scraped when finally, in 1961, Utzon came up with his "key to the shells" spherical solution for building the sails. In this, the sails are based on the geometry of a sphere with the shape of each sail determined by the shape of a triangle carved out of the sphere. Using this model, Utzon and his team worked with engineers Ove Arup & Partners to successful design and build the iconic sails. This plaque outside of the Opera House commemorates this solution and demonstrates its logic. Photo 3 of 14 in Sydney's Surprising Opera House by Miyoko Ohtake

Sydney's Surprising Opera House

3 of 14

The design was nearly scraped when finally, in 1961, Utzon came up with his "key to the shells" spherical solution for building the sails. In this, the sails are based on the geometry of a sphere with the shape of each sail determined by the shape of a triangle carved out of the sphere. Using this model, Utzon and his team worked with engineers Ove Arup & Partners to successful design and build the iconic sails. This plaque outside of the Opera House commemorates this solution and demonstrates its logic.