Perth city skyline Perth is the capital of Western Australia and Australia's fourth-largest city. The most interesting area, and the one most visitors head to, is the city centre, also known as the Perth CBD. This area isn't very big and there actually aren't that many attractions, so you can explore the city centre at a leisurely, strolling pace. What's more, the Perth CBD has free CAT (Central Area Transit) buses running on various routes, so unless you're heading to the suburbs, you basically don't need to buy a ticket at all.