This was Orthanc, the citadel of Saruman, the name of which had (by design or chance) a twofold meaning; for in the Elvish speech orthanc signifies Mount Fang, but in the language of the Mark of old the Cunning Mind.
Do not approach their citadel.
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If the citadel falls, all is lost.
The New York Stock Exchange is a citadel of capitalism.