10 or 15 days I don't know what there's to see, I don't know Australia Sydney is a great city, Melbourne is the temple of speed, but I don't know if there is something else most beautiful...... If u can get urself into a 4 wheel driving trip (they are awesome :) , and yes there are many beautiful places) do it! Some examples are the Cape York trip, Kimberley trip (both of which I have done) and many many more. But this may be difficult to do seeing as u r coming from overseas :( (besides renting one of those Britz 4wd's n buying some equipment for camping etc then booking a tag-along tour)