Native plants and various ground surfaces define these areas and provide intimate viewing conditions. The Garden also houses the Gallery's outdoor restaurant, The Mirrabook. Much of the building is made of reinforced brush-hammered concrete an example of Madigan's philosophy that concrete has as much integrity as stone. In recent years the interior cement walls have been covered with a removable painted wooden skin, and a lower lighting grid has been added to the entrance level galleries. The air filter has the capacity to remove 85 per cent of all dust particles down to one micron.
Air is supplied at ceiling level and extracted at floor level.
The legislation instituting the National Gallery of Australia went before Parliament in 1971 and the National Gallery Act was passed in 1975. The National Gallery of Australia was opened by Her Majesty Queen Elizabeth II on 12 October 1982.