Let's start by locating Babylon. Christians have variously located it in Rome, the Vatican, Jerusalem, London, Washington D.C., the United States or some other various locations. For us to correctly locate it, we will start by studying its adversary and counterpart, the Kingdom of Yahweh [God] or the City of Yahweh [God].

The gospel of the kingdom is the good news that Yahweh's kingdom is here now, all who want can enter in and it is located within us, meaning it is spiritual, not physical.

Yahushua answered, My kingdom is not of this world: if my kingdom were of this world, then would my servants fight, that I should not be delivered to the Jews: but now is my kingdom not from hence. John 18:36

The law and the prophets were until John: since that time the kingdom of יהוה [Yahweh] is preached, and every man presseth into it. Luke 16:16

And when he was demanded of the Pharisees, when the kingdom of יהוה [Yahweh] should come, he answered them and said, The kingdom of יהוה cometh not with observation: Neither shall they say, Lo here! or, lo there! for, behold, the kingdom of יהוה is within you. Luke 17:20-21

Its counterpart, Babylon, Satan's kingdom is likewise spiritual.

Put on the whole armour of Elohim, that ye may be able to stand against the wiles of the devil. For we wrestle not against flesh and blood, but against principalities, against powers, against the rulers of the darkness of this world, against spiritual wickedness in high places. Ephesians 6:11-12

Babylon is a system, not a place; principalities, powers, rulers of darkness, not geography. Satan would like his kingdom to include the whole earth, all of Creation, but he lost that war when he murdered the Creator. His kingdom is now limited to his followers (the citizens of Babylon) and any control they can exercise. Prophetic cities represent "peoples" not places or churches. "Sons of Satan" are his people (see "Babylon, Church or Kingdom?").

And here is the mind which hath wisdom. The seven heads are seven mountains, on which the woman sitteth. Revelation 17:9

Some people point to this verse to show a definite geographical location, claiming that Rome is the city of seven mountains or hills (as are many other cities, see wikipedea here). This may be, but the seven mountains (heads) are on the beast, not the woman, so they have little to do with Babylon and nothing to do with its location. The woman (Babylon) is indirectly sitting on the seven mountains but she is actually and directly sitting on the beast with seven heads and ten horns (Revelation 17:7). She also sits on many waters:

Come hither; I will shew unto thee the judgment of the great whore that sitteth upon many waters: Revelation 17:1

"Waters" are peoples - think the seven seas, or all the Earth.

And he saith unto me, The waters which thou sawest, where the whore sitteth, are peoples, and multitudes, and nations, and tongues. Revelation 17:15

And the woman which thou sawest is that great city, which reigneth over the kings [all the kings] of the earth. Revelation 17:18

For all nations have drunk of the wine of the wrath of her fornication, and the kings of the earth have committed fornication with her, and the merchants of the earth are waxed rich through the abundance of her delicacies. Revelation 18:3

These verses show that there is no geographical limitation to Babylon. This is because Babylon is not physical, it is Satanically spiritual and it exercises power over ALL the earth and ALL the kings of the earth.