I had spotted this place in one of my frequent scans of Google Earth, looking for interesting things to check out. There really weren't any clues from the imagery as to what it was, but I could see that there was a path leading to it. It would all come down the the Mk I Eyeball.
We parked on the side of the street and took a quick hike down the trail to find a set of disused railway tracks. I doubled back, following these to where my map indicated that I should turn off into the bush. And there it was.