The photo below contains GPS co-ordinates to a free campsite near Carlsbad Caverns. Check out the location in the image using the iOS Photo Investigator App.
Carlsbad Caverns in New Mexico is HUGE. I've always been passionate about exploring tunnels, perhaps as a result of an earlier visit here. The entry fee allows you to explore an enormous area on foot, walk down into the entrance (and back out) to get the full experience for the enormity. An elevator also links the main cavern to the visitor center, but avoid this if you can.
From the main cavern you can see this ladder which was used by a National geographic expedition over a hundred years ago to explore the "lower cave":
If you sign up beforehand (or get lucky and it's available the day you show up), tours run into this lower cave, as well as many other areas of the cave. The ranger led tours follow rugged paths, and give a much better feel for the cave, including "black outs" where everyone listens to the silence with lights shut off. Carlsbad Caverns, go!Share on Twitter Share on Facebook