Martin Place, adj. — Green’s Dictionary of Slang

Martin Place adj.

[proper name Martin Place, Sydney; the image of the ‘big city’ as de facto wicked]

(Aus.) in the context of the city, decadent or corrupt, or seen as such by country people.

1938		Bulletin (Sydney) 28 Dec. 19/3: Martin-place outbackers.
1961		Bulletin (Sydney) 1 Mar. 32/3: Wish I was a Martin Place bludger.
1979		S. Moran Reminiscences of Rebel 59: More unusual ones [i.e.. nicknames] were [...] Martin Place (full every lunch time) [etc.] [AND].