Due the giant mana storm over Sydney and being far more enclosed and separate Melbourne has taken over as the most populated city and largest by far.
South Melbourne, St Kilda, the inner CBD and most of the outer inner suburbs like Brunswick, Coburg, Richmond, Carlton have an average of 7 stories with most of the older buildings being converted to new apartment blocks.
Several of the outer/inner suburbs have large apartment blocks with tiny self-contained rooms to house a massive influx of people coming to Melbourne.
While small on the scale of cities around the world the population has still tripled to that of around 15 million people. In an effort to stop urban sprawl the city went up instead of out.