I loved the caves epsiode (being a bit of spelunker myself).
Have to say though I was a bit disappointed with the Lechuguilla footage. Don't get me wrong it was great, but given they were the last film crew ever likely to be given permission to film there they really didn't even begin to scratch the surface (so to speak).
I realised they were leaving the best until last but 5 minutes to show by far the largest known cave system in the world, and the most unusual ...
Mind you all power to them getting 500kg of equipment that far underground - most people would struggle to get themselves there
Thankfully I have a large collection of photos to drool over