Darling Harbour was originally part of Sydney recieving wharfs for trade. The area comprised mainly the rail system servicing the whaves and was completely torn down in the early 1980's to make way for the current incarnation of the Darling Harbour tourist presinct. I found images
here from before the demolition began.
If you've ever wondered about the hideous Pyrmont-City road bridge that looms over such a lovely place, this picture may explain why it seemed like no thought was put into the placing of those monstruous structures: