At the co-ordinates provided, look at the sign. The key required to solve the cipher (below) is the word next to the Crown.
EWLOLHONERIECDPHHESDITCOMSNUKUNUNTRHGIIGNTLTEOEFRFEHEHGL
Once you decipher this message you will obtain the final piece of infomation required for locating GZ.
Now make your way to where Belgrave intersects Kensington (streets in Kogarah). Stand upon this cross and look into the distance. Seek and you shall find.