johnw wrote:I can't recall seeing this before. The rock looks like that in the limestone karst area around Blue waterholes/Yarrangobilly etc.
But the hole looks too neat for a natural cave. More like a mine adit or maybe a tunnel related to the Snowy Mountains hydro scheme?
It’s natural as far as I know. I’ve been inside the cave. You are pretty close John. Not many people come down this way