Begin your process by researching Australian architecture, and finding what makes it so unique. Use the sources below to explore, but remember you are not limited by these. Google search anything that strikes your interest, and see where it leads you. Also, don't narrow your searches; look at the old just as much as the new. Perhaps you could compare buildings from your hometown to those of Australia (libraries, schools, public buildings, etc.) Then, after you have a feel for the architecture and what it has to offer, choose a timeframe of architecture you want to learn more about. After researching a specific time of Australian architecture, find a piece that represents your research to explore even further. Find out why it was built: for what purpose? Look for its architect and location. Does it fit in with its surroundings, or is it a statement to be made. Explore its individuality and find what makes it so appealing. You want to have enough material to work with to create your advertisement, and make others want to get on a plane and fly to visit australia that second. Use what you have found to create your informative, and intriguing advertisement to present to the class. All presentations are individual; there are so many interesting pieces of Architecture, you shouldn't have any problem finding one that interests you.
Some works that might be of interest include: Ian Thorpe Aquatic Center, Federation square, The Big Lobster, Sydney Harbour Bridge, Royal Exhibition Building, Parliament House, and Avondale Heights Library & Learning Centre.