I think I would rather live in a tree house than underground (unless by underground this question means a Hobbit hole…) I always wanted a tree house as a kid. I was really jealous of my neighbor’s fort (it was so cool, it had a ladder, 2 slides, a balcony, windows with shutters… Like I said, cool!). Occasionally I watch the show, “Tree House Masters”. Some of the designs on that show are really, really cool. As for underground living, I have visited the Natural Bridge Caverns in San Antonio, TX; which are really fun to explore. However, in the end, I still think I would rather live in a tree house.