A very impressive spectacle: A huge cave deep inside the mountains, unlike anything I have seen before. The caves have been used by Cherokee Indians and during the Civil War as storage for weapons.
Lower down the caves lies the Lost Sea: The largest underground lake in the US and the 2nd largest in the world. The feeling was amazing and horrifying ta the same time. A 13 year old kid first discovered in in the early 1900's when he sneaked through a tiny hole during a summer when the water level was low. The tunnel led him to the above hidden cave. When he went back to tell the story, none believed him because it seemed insane and he was fond of telling lies in real life. Therefore the sea was lost for about 50 years until future expeditions rediscovered it.
There is also and underwater tunnel that leads to a separate room, which is filled with water until the very top. When divers went there the air bubbles they released had no room to escape, increased the pressure in the chamber and the ceiling fell!
The most interesting thing in the cave for me though was the weird experience of absolute darkness. There are only 2 places in the world where absolute darkness can be experienced: in the bottom of deep oceans and inside deep caves. When the tour boy suddenly turned off the lights, I was shocked. I could not see a single thing. It takes about 6 photons to activate one cell in the back of the retina, and at no time did this happen. It was 100% absolute black.
In fact, if you spend 2 weeks in this place of absolute darkness then you become blind because of your eyes failing to acquire light. As I was moving my hands in front of my face trying to see them, I thought I saw something that seemed like the shape of my fingers. I now realized it is our brain that did that: it thinks that since the hand is there the eyes are supposed to see something and nevertheless some relic image is projected although there is no real input. I have tried this thing with specialized pictures online and in fact it works well, but this was the real thing.
