Don't attempt this cache directly from the road or from above. Don't stop your car on the main road either! I have provided a parking waypoint at S34 29.996 E150 24.397. From there it's a short walk to GZ.
I took a wrong turn on International Geocaching Day 2019 and happened across this location which reminded me of one of my other caches out near Colo Vale. So I have created a similar cache here.
Park at the parking waypoint (S34 29.996 E150 24.397), walk across the park and you should see the entrance to the tunnel. The cache is an easy find at the other end. If it's been raining, you might need your wellies.