The Castle in the Air is where the princesses Rhyme and Reason are imprisoned. Located at the top of a perilous, wind-swept spiral staircase that rises from the highest peak in the demon-controlled Mountains of Ignorance, the Castle is supremely hard to reach. Milo, Tock, and the Humbug overcome all obstacles, reach the Castle, and bring the princesses back to Earth. “Castles in the air” is an expression that describes things people would love to have that are nearly impossible to obtain. For Milo, who began his journey with no dreams or ambitions, the Castle in the Air becomes his grand quest, a way to contribute to the betterment of the Lands Beyond by returning to it the sanity of Rhyme and Reason.

The walled, gated city of Dictionopolis is the capital of the word industry. The city’s orchards grow letters that are sold at a weekly Word Market. The ruler, King Azaz the Unabridged, and his subjects believe that words are more important than numbers, which are mined in the competing city of Digitopolis. The split between the two cities, and the imprisonment of the princesses