Adventures of a Digger

Extract from the collected diaries of "BHV the Great Explorer":

"It was during one of my summer treks of 2013 through unmapped territories that I became separated from my travelling companions and came upon a curious thing.  It was a cave of sorts, but by no means one of natural origin.  It was formed of an almost perfect circular cross-section and its sides were somewhat pinkish in colour.
As I ventured inside, I felt an eerie quiet descend around me and a general feeling of foreboding. But press on I did and soon found myself approaching what looked like some sort of cave-in blocking my passage. On the wall ahead of me was painted a large letter 'Y', above and to the right of which was a single eye. These things are common in places of mystery and treasure to keep out those of a superstitious mind, for the eye was expertly painted to display the illusion of following me as I approached.
As I came nearer to the large painted artefacts, I reached forward to place my hand on the letter, only to discover that it was no painting at all but some sort of vent, for out of it came a sudden rush or air and from behind it I heard a loud thump.
Well I am afraid to say that the sudden noise pushed me to fear, so I quickly turned tail and ran like a frightened child, not looking back.
The mystery of that cave haunts me to this day, though I did manage to acquire one clue as to the goings on of that strange place. This one photograph taken before I was startled so."

"Later that day, on finding my colleagues, it appears that the area was awash with these mysterious caves, although I understand that the cave they found was blocked from the entrance.  I guess that some mysteries are destined to never be unravelled."

[Note from the editor:  The following photo was later recovered from the camera of the BHV's travelling companions, clearly showing the cave and the strange obstruction they encountered.]