So, while various things described in the Book of Revelation could very well be allegorical in nature, this passage here does seem to be eerily concrete.
Revelation 10-11, 16-19, 21
Standing afar off for fear of her torments, saying: Alas! alas! that great city Babylon, that mighty city: for in one hour is thy judgment come.
And the merchants of the earth shall weep, and mourn over her: for no man shall buy their merchandise any more.
...
And saying: Alas! alas! that great city, which was clothed with fine linen, and purple, and scarlet, and was gilt with gold, and precious stones, and pearls. For in one hour are so great riches come to nought; and every shipmaster, and all that sail into the lake, and mariners, and as many as work in the sea, stood afar off. And cried, seeing the place of her burning, saying: What city is like to this great city? And they cast dust upon their heads, and cried, weeping and mourning, saying: Alas! alas! that great city, wherein all were made rich, that had ships at sea, by reason of her prices: for in one hour she is made desolate.
...
And a mighty angel took up a stone, as it were a great millstone, and cast it into the sea, saying: With such violence as this shall Babylon, that great city, be thrown down, and shall be found no more at all.
So, there are multiple references to a great / mighty city, and it's destruction comes suddenly (within one hour), with such force that an angel (in St. John's vision) hurls a giant millstone into "the sea" to demonstrate the force with which the city (with such violence as this) would be destroyed and "found no more". You can imagine the water spewing up after the millstone hits it. Except that it's also referred to as "[the city's] burning". So a violent burning with tremendous force. In addition, there's reference to this somehow being a great financial center of the world: "merchandise", "merchants shall weep". We've mentioned above how, to the South of the UN building (per the seer of Krems) is to be found ... Wall Street, the stock market, and I'm sure a huge percentage of the US financial and banking system.
Finally, last, and the opposite of least ... the image here mentions "every shipmaster", "and all that sail", and "mariners", and "as many as work in the sea" ... stood far off, or perhaps meaning at some distance, where it almost conveys an image of them standing there watching the city burn.