Examples:

• An ice castle in the air, the best and the brightest frozen solid.
• A little castle in the air.
• An ice castle in the air, the best and the brightest frozen solid.
• It is nothing more than a castle in the air - an illusion which melts like the mist.
• Take me with you To your castle in the air
• The grandiose announcement of a new Employment Pact turned out in reality to be a castle in the air.
• It is no castle in the air, but a long overdue, concrete attempt to go beyond employment guidelines and achieve co-ordination of economic policy within the European Union, particularly with a view to promoting growth.
• Although one of the publishers—Elsevier—has now restored access, some poor countries are beginning to feel they have been given the keys to little more than a castle in the air, built on a non-binding agreement that can be withdrawn with little notice.