Some fellow buys an abandoned cave dwelling and does it out. One of the more interesting ones as opposed to yet another glass box.
However, I think he'll come unstuck in Winter, sure to be water leaking in. We had a dry Summer. It was abandoned for a reason.
I wonder how you do a heat loss/U value calculation when the thickness of the "walls" is effectively infinity?
All that moisture evaporating will cause a massive cooling effect.