The diagrams compare some changes in two distinct underground tunnel systems of Australian cities over time.
The cities have changed over time, with the introduction of new infrastructure, which can be seen in the second diagram. The main developments are that the city is more advanced and accessible to the public.
Looking at the maps in more detail, we can see that the roads have been built to accommodate the citizens of the city. The other physical structures that have been added are new buildings, a school, a hospital, and a cafe for the communities. The underground passage has been constructed with stone and clay, 2.5 meters in width and 3.6 kilometers in length. Before, the city was completely bare apart from these developments.
In contrast, the first diagram depicts that there used to be a bridge over the water body, and the ground was covered with sand. The parking area was built for $555 million, which had increased by 2006 to a cost of about 1.1 billion.