None of them*. They are all listed on the World Heritage register because of their "outstanding universal value".
Australia has 16 World Heritage areas and properties, including sub-Antarctic islands to fossil deposits to tropical reefs and rainforests . Most have been declared significant because of their natural and/or cultural values but only one was declared on the criterion of architecture and technology.
The Royal Exhibition Building was constructed for the international exhibitions of 1880 and 1888. The architect, John Reed, mixed together a range of styles from Byzantine to Renaissance to produce a magnificent and functional display space. (John Reed also designed Trades Hall, the State Library and Rippon Lea, among others. The firm he founded still produces remarkable work, including the Crown Casino and Federation Square.) Museum Victoria continues to use the building for trade exhibitions**. In 2007, it's hosting the Hot Rod Show, travel and art expos and an organic produce show (in which I had a glimmer of interest until I saw the neologism 'eco-ganic').
(I should point out that the top photo is of the western side of the REB and the bottom photo of the northern side. But that's where the sun was when I was there. The main entrance is to the south.)
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*Yes, it was a trick question. Not much of one, I'll admit, but I have low standards.
**I think they've stopped the rave parties.
