About 20 kilometres from anywhere resembling a town in the south-east, a inconspicuous dirt road cuts through man-made forest to the most ominously-named sinkhole of them all. Despite the popularity of other surrounding cenotes, there s not a single person to be seen on the road, or at the park from which a pathway leads to a shaggy and distinctly out-of-place patch of bush. It s eerily quiet when I reach the hellmouth, which has been made accessible to visitors by an enclosed steel bridge which juts over the top of the sinkhole, the height from which makes me instantly woozy. I clutch my new iPhone a little tighter, brave a few quick shots, and then scuttle back to the safety of my car, just in time to see an entourage of visitors arrive. Hells Hole is 45 metres in diameter, 25 metres deep and it s 38 metres to the water from the viewing platform. It s a popular site for diving, and permits can be obtained through ForestrySA. The similarly accessible Caroline Sinkhole is a