Don't take the elevator. It's fast, but if you are in even somewhat good shape take the long way in. The path is steep with lots of switchbacks but it is not slippery and if you take your time you won't have trouble walking in. Be sure to buy the audio self-guided tour at the gift shop. It is very good about explaining every transition as you move from daylight to the great room. Go early before there are too many people on the path. For some reason there are always those who like to rush past you rather than take their time and look around at where they are. There are bigger caves, longer caves, and deeper caves, but non as beautiful as Carlsbad Caverns. By taking the natural entrance in you pass through the 'twilight' zone and get a complete cavern experience.