never-never land

Proper noun

 * 1) A fantastic or imaginary place.

Usage notes
One is said to be "off in never-never land" when one is coming up with completely impractical ideas, distracted, etc. "Going to Never Never Land" can also mean going to sleep, or, more darkly, dying.

Compare also "the Never-Never" as a term referring to remoter parts of the Australian outback.