It was taken inside a "tunnel" which has been formed by a large chunk of the rock cracking off, sliding down the side and leaving a cavity underneath. So in the photo, the primary rock is to the left, the sheet that has slid off is to the right.
The sheet of rock that has slid off would probably be about 60-100m long at a guess, and enormously thick and heavy. It would've made one big thump!
The tunnel is curved slightly and long enough that when inside there is some distance where there's very little light and you can't see either end. Quite speccy
Roger.