The concrete shells were produced by cutting a three-sided segment out of a sphere. The roof shells and their vaulted concrete ribs were pre-cast and held together by pre-stressing steel tendons, an innovation at the time. Utson commented that this resolution of the spherical roof-shells ‘gave way for a very logical and orderly geometry for the tile lids that were to cover the entire surface of the shells'.
The tiles were a major item in the building. 'It is important that such a large, white sculpture in the harbour setting catches and mirrors the sky with all its varied lights dawn to dusk, day to day, throughout the year.' The citation from the American architect Louis Kahn describes the importance of this surface and of the decision to make the surface white:
The sun did not know how beautiful its light was, until it was reflected off this building.
~Louis Kahn
