It'd be fun to build one of these!
"Some features of the Eco-Dome include:
1) Built from local earth-filled Superadobe coils (soil-cement or lime-stabilized earth).
2) Tree free.
3) Maximum use of space through alternative options.
4) The main dome and four niches, depending on local code approval, can function as:
a) main living room, entrance hall, kitchen, bathroom, bedroom (called "bed-womb" because of it's small, organic form!)
b) living room, entrance hall, and three bed-rooms.
c) living room, entrance hall, two bedrooms, and a bathroom.
5) Self-contained single unit (potential for a guest house or studio apartment).
6) Can be repeated and joined together to form larger homes and courtyard houses.
7) Can be built by a team of 3-5 persons.
8) Designed with the sun, shade and wind in mind for passive cooling and heating.
9) Wind-scoop can be combined with a rated furnace unit, depending on local code approval.
10) Interior furniture can be built-in with same material."
"As a rule, they were dumpling-shaped, built of mulch, silt, stray divots, and other seasonal deposits, often whitewashed by irregular pigeons. Consequently, most boggie towns looked as though some very large and untidy creature, perhaps a dragon, had quite recently suffered a series of disappointing bowel movements in the vicinity."
-- "Prologue: Concerning Boggies," from _Bored of the Rings_ by Henry N. Beard and Douglas C. Kenney.
Y'know, I was actually going to ask about the load-bearing capabilities of this type of structure, to figure out if it was feasible to shovel a hill on top of one of these and call it a hobbit hole - but somebody essentially beat me to that corner of the noosphere, then went further....