Answer:
Those details help establish the setting because:
A. They give the sense that nature has taken over a once-urban area.
Explanation:
This question is about the short story "By the Waters of Babylon", by Vincent Benét. The details mentioned, "stone or metal,” "many pigeons,” "towers,” and "wild cats that roam the god-roads,” appear once the main character, John, arrives to a forbidden place. John is a priest in a post-apocalyptic future. After mankind has destroyed most of itself by misusing technology, the remaining social groups retrogress to a more primitive way of living, filled with superstitions concerning metal.
The forbidden place where John arrives is New York City, or at least what is left of it. Nature has taken over, reclaiming the space that had previously belonged to it, before man arrived and conquered. Now, the streets (god-roads) are paths where wild cats roam. The towers (buildings) serve as nests for pigeons. There is no sign or "smell of man left, on stone or metal." Nature has conquered this once-urban area back.
