Make sure you get to the visitor center before 2:00 p.m. if you want to enter the caverns via the natural entrance. I arrived at 2:20 p.m. and missed the opportuity. I had to take the elevator down to the main cavern, the Big Room. The size of the cavern is massive but it is diffucult to imagine that the cavern is the size of 7 football fields because the spot-lighting is too subtle. The flash from a camera washes out a lot of the features. During my visit in April, the bats were still on their way to the cavern from from Mexico so the night time bat viewing program was not operating.