they're actually split in half - from south to north:
Flinders St - [Flinders Lane] - Collins St - [Little Collins St] - Bourke St - [Little Bourke St] - Lonsdale St - [Little Lonsdale St] - La Trobe St.
from west to east the major blocks are split up by the myriad of lanes that have existed (and many changed since then) since the original settlement in 1835.
in this photo you can see Little Collins St at the base of the old ANZ HQ (brown building on Queen St), and you can [just] see McKillop St (the red coloured site then there's one building abutting the site then the laneway entry) which is one of the heavily pedestrianised lanes in the west end just coming off Bourke St
But yes a relatively major contrast to many north american cities where skyscrapers can form one city block (or only 2-3 buildings on one block) - prime example Chicago etc.