The amphitheatre is huge! Those small shrubs shown leaning over the gap in the roof are actually full sized Eucalypts!
During the wet season water flows in through a creek entry on the far side. But the exit (that people use to enter the space) is much smaller than the entry for the water. Water builds up and swirls around inside the space - picking up rocks etc which then carve horizontal scratches on the walls.......
This collage shows Errol entering, the floor, 2 walls of the amphitheatre and the hole in the roof.
@ludwigsdiana Hi Diana - thanks for your nice comment - and it was so huge that it was virtually impossible to get all of it in one photo. A fascinating place. :)
@jgpittenger LOL Thanks Jane - you must have all seen that white hat many times by now - he's always out the front - I'm too slow - back there taking photos! And, as you said, he is good as a scale indicator. Cheers Rob