There was a period in my life when I was actually seeking a finished cave to live in. This specific cave house was one that I greatly admired at that time, which was not that long ago. If I had the chance and monetary funding, I would live in a kick ass cave. No doubt. I have been to this home (under construction) several times before the sale on Ebay in Festus, Missouri.
http://www.fun2fun.info/2009/02/26/festus-missouri-cave-house-for-sale-on-ebay/