Here is a link Woolley, it is anything but flat!
Basically, because of the permit they run this like a rally, but always on the same stage.
Our "regular" hill climbs are generally like the UK, single ribbon of tarmac (though I know of some dirt ones) over an undulating course between about 600 mt and 1200 mt.
The notable exception is Bathurst. They actually use the circuit at Bathurst in reverse direction going up through the dipper, have done so since the 20's, ie before it was used as a curcuit.