This is one of the coolest free things to do in Las Vegas.
Unfortunately, I just heard that it is closing. I'm very glad that I had a chance to visit before it went away.
When I was there, the lions were sleeping on top of the glass walkway, so you could look right up at them just a few inches away. There were two human trainers resting with the cats in the habitat, petting them as they slept.
I can't say that I'd want that job.