What “city” is meant at Gen 11:4?

And why was this of significance both for the current narrative and the rest of the Bible? We are told, in fact, that it was “Babel,” and this understood to mean Babylon. This is significant as being the first city mentioned in the post-Flood world (being first listed at Gen 10:10). Babylon later became the nemesis of Israel and a symbol of decadence. It became if anything an even greater and more proverbial symbol of decadence by New Testament times.