The last description of the woman is the great city. It is the key to understanding the harlot. Is this a particular city, say New York or Rome, or is it a generic city with a large population? The early countries had only one city that dominated, like Rome. Phoebes and Egypt, Assyria and Nineveh, Babylon, and Rome. But as Rome changed into the Holy Roman Empire and into Europe, there became many large cities. Rome continued in many forms until the role was passed on to the seventh head. What made Rome any more wicked than Paris, Amsterdam, or Berlin? It is the wickedness, not the location, that makes it evil. I can only conclude that "great city is a name for all large cities within a country, and they also sit on many waters. If any one city within a large country like China, the USA, or Russia was destroyed, the effects would be noticed but not destructive to the country. The city that has fallen is Babylon, but it can never truly be destroyed until all large cities are destroyed. In small places or countries, people with strange ideas or wicked tendencies get little opportunity to meet others with the same problems. So wicked behaviour is naturally contained. When you have a considerable population, it is easy to find others with the same issues. Together, they then go deeper into evil opportunities. Bad behaviour loves company. It is simple mechanics that explain why large cities become profoundly wicked. And that's before you add all the spiritual influences.