It's a vastly complex machine for keeping its inhabitants alive and somewhat happy. Natural selection allows machines of such complexity to arise of their own accord, but in this case, since humans are involved, one might prefer to think that Melbourne was designed to the best of human ability to achieve its purpose.
However, this is misleading. Actually, Melbourne arose as the result of millions of individual agents acting, often in purely their own interest (with some exceptions), usually in the short term (again with exceptions).
Does this matter? Well, yes, because Melbourne is actually not a very efficient machine. Take cars, for example. Melbourne could transport its inhabitants very much more efficiently using various modes of public transport. Cars are what happen when a bunch of more-or-less selfish humans get together in the one place, but they are not in the collective best interest of those humans.
I think this is an important class of phenomena, and that mistaking this class for the result of intelligent design is a common error. Furthermore, it is and error that leads to wholly inappropriate attempts to fix the problems this class of thing causes.
Take capitalism, another example. It seems to be a vast conspiracy to reduce us to consumer wage-slaves and despoil our environment for the benefit of, say, some power hungry cartel of shadowy capitalist overlords. If we could just expose this cartel, denounce it, destroy it, surely the world would be a better place. Except there isn't such a thing, there is just us, a bunch of individuals making individual choices.
Here's a third example: nature itself. Nature exists in an intricately beautiful and complex state of self-balance. The beauty of its parts distract us from observing that the whole is actually rather awful. Predators chasing prey, for example, is a wholly pointless phenomenon. Plants that go out of their way to be hard to eat. Parasites. Viruses. Nature is no more ideal than Melbourne. It would be possible to design something better.