Wonders in the Earth

An amazing crystal cave... can you see the men above, in orange, crawling around on the 30 foot crystals?  The cave is also very hot with 100 percent humidity... you can drown just by breathing in this place.

Nigel and I intrepidly stepped forwards – to say that the heat hit us like a wall would be an understatement, my glasses steamed up and their metal frames almost burnt me - I had to leave them at the entrance. A slightly fuzzy view however did not perturb my sense of awe. I was dumbstruck. A torrent of sweat streamed from my head, my energy was being sucked away, and my breathing became heavy. The view was enthralling, my eyes led me forwards but my body wanted to retreat. I was dwarfed by a forest of giant gypsum crystals, some up to 12 metres long - the largest crystals ever discovered, some estimated to weigh as much as 55 tonnes. It was something that had to be seen to be believed and I was doing just that... however within just five minutes I had gone from a reasonably fit 30 year old to an asthmatic 60 year old

What other wonders lie beneath our feet?