Anybody here ever try to make their own underground/earth cooled/heated home?

Have you ever tackled that kind of challenge? How much did it cost? When did you get around to doing it? How long did it take?

I'm curious about alternative home owning methods and It struck me that a lot of the long-term cost of housing is electricity, water access, and overall material cost like roofing, flooring, walling, and labor cost.

Is it practical to make a big hole in the ground and work with that space, or at the very least find a hill and build a house into the earth that way? I know it's possible, but has anyone here actually done it?