Tis easy to build castles in the air.

Meaning: Imagination costs nothing, but translating dreams into reality requires effort and resources.

Origin: The older image was "castles in Spain," from the 13th-century French Roman de la Rose, for daydreams of things one would never own. "Castles in the air" replaced it in English in the late 16th century. Henry David Thoreau gave it a hopeful turn in Walden (1854): 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."

Equivalents in French, Spanish, Japanese, German, Italian, and 4 more languages

French: Faire des châteaux en Espagne (literally: To build castles in the air)
Spanish: Hacer castillos en el aire (literally: To build castles in the air)
Japanese: 絵に描いた餅 (E ni kaita mochi) (literally: A rice cake painted in a picture)
German: Luftschlösser bauen (literally: To build air-castles)
Italian: Fare castelli in aria (literally: To build castles in the air)
Dutch: Luchtkastelen bouwen (literally: To build castles in the air)
Russian: Строить воздушные замки (Stroit' vozdushnye zamki) (literally: To build castles in the air)
Polish: Budować zamki na lodzie (literally: To build castles on ice)
Chinese: 空中楼阁 (Kōngzhōng lóugé) (literally: A pavilion in the air)