I loved Carlsbad Caverns in N. Mexico. If you go to northern N. Mexico I would recommend slipping into Colorado to see Mesa Verde. Obviously you should see the Grand Canyon - fabulous. We also loved Zion & Bryc National Parks in Utah. If you are going to visit more than one of these parks, I recommend purchasing an annual National Parks pass. I think it is $80 but it gets you into all of the National Parks for a year - well worth the money. I have done this trip more than once so PM me if you have any questions.