Well my WIIW this week was an easy peasy one!
Marcy said: "Grillwork in an entry of some historic
landmark?"
Well that is worth 100% + bonus points for the extra
information it is an historic landmark!
Jennifer (AKA Old Kitty) said: "Ooooh it's a doorway to
one of the old post offices!
It is an old doorway 100%, but no bonus points because it
isn't a post office.
And Linda G said "It's a doorway. ;) "
That is exactly right it is a doorway, 100%
So what was the mystery building?
I have posted about this place before...
Like the Eiffel Tower in Paris
this structure was built as a temporary affair for an International Exhibition.
To be precise the 1880 Exhibition when Melbourne
was the richest city in the world (thanks to 30 years of gold-rushes) and
wanted to show off. 
Half of the structure was demolished at the end of the
exhibition but a last minute change of heart saved the rest.
The Royal
Exhibition Building had a brief break from its normal duties in the early part
of the 20th Century when it acted as the first home of the Commonwealth
Parliament of Australia (our second and third Parliament buildings are in our
Federal Capital Canberra).
But since then
it has returned to its original duty as the site for around 300 days of shows
and exhibitions each year. 