We hiked down the Natural Entrance, did a self-guided tour in the Big Room and ranger-guided tour in King's Palace. I think the best is the Big Room. The King's Palace tour was good too but ranger did not want people to use tripod because it may slow down the group.
In terms of photography, I think this place is HDR's heaven. So bracket your shots and play your HDR program later. You may get some amazing effects. Also do not forget to bring a gray card for white balance.
There is not much to see on the ground as this is an underground park. We drove the scenic loop but it was not impressive at all.
Big Room
Big Room
Big Room
Big Room
Big Room
Big Room
Rock of Ages
Twin Domes
Painted Grotto
Painted Grotto
Natural Entrance
Big Room