She tells me she's planned out her whole career, but as far as I can see it's all just castles in the air. CIDI
Of course Francis had thought about it as something that was inevitable, and he had plans, but they had never seemed very real and he had looked on them as castles in the air. BNC
I remember the days when, as a small child, I was taken around boatyards, harbours and rivers to admire boat after boat, while he built castles in the air about owning one. BNC