Kitty -

Andymac is correct about the first two.

Coober Pedy is a town in the desert in South Australia where they used to (and still do) dig for opals. It's so hot out there that just about the entire town is, like the opal mines, underground. The walls, floor & ceilings are made of earth.

Haven't heard "You come back to Tassie" so I can't help you there.