Not really a street circuit as such or an original design, this circuit hosted the Australian Grand Prix in 1939 around the town of Lobethal in the Adelaide Hills.
An onboard lap of the circuit: http://www.youtube.com/watch?v=mQZqAVvfsJk
At 14km long its the longest circuit ever used in Australia. I think it would be better suited towards an endurance race although realistically it would never happen.
One can dream though :P