Sir Walter is famous for a lot of things.
Canberra springs immediately to mind, however there are some local examples of his architectural ideals.
The nearby town of Griffith was designed by Sir Walter and you can see that in the prevalence of roundabouts and long, linear roads.
Sir Walter Burley-Griffin designed the two water towers for the town of Leeton and they're well worth a visit.
You might want to be stealthy, as it's near one of the main roads in the town and in full view of the nearby ambulance station.
Please make sure you put the cache back exactly where you found it.
Good luck!