Cloud cuckoo land
（重定向自Nephelococcygia）
Cloud Cuckoo Land refers to a state of absurdly over-optimistic fantasy or an unrealistically idealistic state where everything is perfect. Someone who is said to "live in cloud cuckoo land" is a person who thinks that things that are completely impossible might happen, rather than understanding how things really are. It also hints that the person referred to is naïve, unaware of realities or deranged in holding such an optimistic belief.