I had a notion of a house that emerged from the grass...you could walk on the roof, lounge, hang-out, play frisbee, but don't fall off the other side, unless it's into the pool!
I understand that these actually exist to an extent, as part of the whole "green energy" initiative... There are homes that are built halfway into the ground so that the earth acts as natural insulation in both winter and summer. There is also "sod roofing," where a special frame holds a layer of dirt and grass on top of the house, again as a form of insulation... It is also supposed to require less frequent maintenance than traditional roofing.
For some reason it reminds me of Iron man's place in the movies.