build castles in the air

verb

Etymology: The first term dates from the late 1500s. A variant, castles in Spain (or châteaux en Espagne), was recorded in the Roman de la Rose in the 13th century and translated into English around 1365.

1. To have any desire, idea, or plan that is unlikely to be realized; to imagine visionary projects or schemes; to have an idle fancy or a pipe dream; to daydream.

   “Look you, Amanda, you may build castles in the air, "and fume, and fret, and grow thin and lean, and pale and ugly, if you please." But I tell you, no man worth having is true to his wife, or can be true to his wife, or ever was, or will be so.”

   “If you have built castles in the air, your work need not be lost; that is where they should be. Now put the foundations under them.”