air castle

So I would imagine it's a lot like jumping on a bouncy castle, one of those air castles, that kids play on.

Although Johnny might have been more cordially received by Merchant Lyte, he was satisfied enough with his welcome to build up air castles.

Even the metaphysicians who build their unstable air castles on à priori ideas declare these ideas cannot be matters of mere intellectual perception, but must be intuitions of the higher reason.

I think sometimes if I could see these beautiful places and run around among the flowers, how happy I should be; but that is one of my air castles.

From the strong sweep and stroke and virile outline of a Brangwyn or the gnomesque possibilities of a Rackham, the great mountain softened to the ethereal air castle of a Parrish.