never-never land 
noun
An imaginary utopian place or situation: a never-never land of unreal prices and easy bank loans...
- I praise the aspirations of the girls I have just met and say that it is heartening to hear that they are reaching for professions rather than the never-never land of pop and modelling fame.
- Those two jokers may be happy in their never-never land, but it's time they recognised reality.
- The venerable Disneyland Hotel has transformed much of its outdoor space into a never-never land with a pirate ship, a mermaid lagoon, and tropical landscaping.
Origin
Early 20th century: often with allusion to the ideal country in J. M. Barrie's Peter Pan.