Quotes below from: http://derrenbrown.co.uk/blog/2009/12/deadliest-place-earth/
"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 – it is the antithesis to the elixir of life!"
“It’s [122 degrees Fahrenheit] and has a humidity of 100%, less than a hundred people have been inside and it’s so deadly that even with respirators and suits of ice you can only survive for 20 minutes before your body starts to fail. It’s the nearest thing to visiting another planet – it’s going deep inside our own."