English idiom "building castle in the air" what is the best translation in Chinese?

Question

Building castle in the air an imaginary dream which impossible to fulfil . What is the best phrase or substitution in chinese translation?

Answer 1

空中楼阁; 幻想; 空想

I give you three translations, and I think the best one is the first 空中楼阁.

Answer 2

You can say "作夢" (which literally means "to dream") or "作白日夢" (to daydream).
e.g. 1. 他不願努力就想成功，簡直是作白日夢。
(He wants to succeed without working hard; he is really daydreaming!)
2. 別作夢了！這是不可能達成的願望！/ 別作白日夢了！這是不可能達成的願望！(Stop dreaming! This is a wish that will never come true! / Stop daydreaming! This is a wish that will never come true!)