The tour lasted 1.5h during which we walked 1 mile through 4 highly decorated chambers. At one time point the ranger switched off all the light and we were sitting in a complete darkness for a few minutes. No matter how hard you try then, you will see nothing. If you see something, it is your brain playing tricks on you.
Below are a few photos that I took during this tour:
Other posts about Carlsbad Caverns.