Tunnels

[Mforcer]

I can't think of any major Australian city near a mountain requiring tunneling.

Australia is an amazing flat country and our mountains are so gently sloped that any boring machine would drive over them before boring into them

A little off topic (it's my thread!), the tunnel on Sydney's Eastern Distributor was the widest double deck box tunnel in the world at the time it was built. I also believe the Sydney Harbour Bridge was the longest spanning bridge of its type when built.