"The Silver Age era of comc book publishing. This is when the Fortress of Solitude was introduced. An idea taken, or ""borrowed"" from the pulp fiction character, ""Doc Savage"". Everyone copies everyone else, or so it would seem. Superman's comic book Fortress had a gold Sun door and gold key. It is a mountain like the image of Olympus. Here is the fabled ""Home of The Sun"". Here the axis mundi about which the Universe spins. Here the source of ""God's love"", pouring out into the world.  These ideas are suggested by the overall mythic imagery and themes."
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