CASTLE

[noun] [C] - a large strong building, built in the past by a ruler or important person to protect the people inside from attackNowadays a castle in Scotland can cost almost the same as a flat in London.Castle is also (informal) for rook (GAME PIECE).The phrase castles in the air means plans that have very little chance of happening.He's always building castles in the air about having a big house and a fast car.