Mermaids Cave is a rainforest gully very close to the town of Blackheath in Oz. When you're there you could be in the middle of nowhere.
Parts of Mad Max 3 were filmed there and it must have been quite a job lugging the equipment up and down each day, as it can only be reached by a very narrow and steep set of stairs.
It's very lovely and the small waterfall is now flowing after the recent rain and the rocks are covered in moss again, with small, delicate ferns sprouting all over.
I managed to slip on a rock and break the new sunnies, but it was worth it.