In "By the waters of Babylon", the Place of Gods is actually New York City destroyed by a nuclear war. John and his people don't know this, that it was a city constructed by men and not gods, because a great deal of knowledge of the doomed civilization was lost. He realizes this through an epiphany.
The Place of Gods is similar to Babylon in the way that the latter one used to be the superpower of her day but this didn't save her from decline. New York City represents the superpower of today, the United States, but this doesn't mean they won't decline, such as every empire before.
When John enters the Place of the Gods, he starts to assimilate that all that he was told about the Place of the Gods is not true at all. The Place of the Gods he visits can be seen as a post-apocaliptic version of the city of New York; because of that, the author is placing the reader in a possible future of ourselves. The portrait of New York as a post-apocaliptic city that we must encourage to build again (by the words of John) can be related to the fall of the city (kingdom) of Babylon in the ancient Mesopotamia.
