Cloud Cuckoo Land in English is a term often used to describe an unrealistically utopian idea of how things are.
You're living in Cloud Cuckoo Land.
However how did the term get started to be used? Who coined it or made it popular?
It originally came from an Ancient Greek satirical play by Aristophanes (The Birds 414BC), in which the original Greek Νεφελοκοκκυγία was often translated as Cloud cuckoo town until the early 1900s. In the play it is a town (or city, more exactly - but it's Ancient Greece, so we're not talking London or New York here).
The 20s and 30s saw a sudden upsurge in the "Cloud Cuckoo Land" form. I think initially this was particularly in political invective (newspaper, radio, later tv). Possibly because the supposedly 'erudite' association with classical learning prevented it being deemed 'unparliamentary language' in Britain (or the equivalent in the US). Later usages diverge somewhat from the exact nature of the satirical original; they often just mean "unrealistic to the point of insanity", with no recognition of the aspirations for "social justice" those early birds forlornly hoped to achieve.
I can't resist quoting from the Wikipedia link above. Remember it's a play competing with others for accolades at its inaugural performance in the 414BC festival (open air, doubtless). After some rather surreal law-making, the birds deliver a parabasis (aside from playwright to audience), which "ends by advising the festival judges to award them first place or risk getting crapped on".
I like that bit! Aristophanes's play actually lost out to Ameipsias's Comastae at that City Dyonisia; I'd like to hope some real birds did the dirty deed!
@FumbleFingers is mostly right. It's from Aristophanes' The Birds, where they are building Νεφελοκοκκυγία (Nephelokokkygia), literally "cloud-cukoo-place". Schopenhauer revived it as Wolkenkuckucksheim, lit. "cloud-cukoo-home" but the -heim suffix is common for German city names.