1 Then one of the seven angels who had the seven bowls came and spoke with me, saying, "Come here, I will show you the judgment of the Great Harlot who sits on many waters,"
2 "with whom the kings of the Earth committed acts of immorality, and those who dwell on the Earth were made drunk with the wine of her immorality.''
3 And he carried me away in the Spirit into a wilderness; and I saw a Woman sitting on a scarlet Beast, full of blasphemous names, having seven heads and ten horns.
4 The Woman was clothed in purple and scarlet, and adorned with gold and precious stones and pearls, having in her hand a gold cup full of abominations and of the unclean things of her immorality,
5 and on her forehead a name was written, a mystery, "BABYLON THE GREAT, THE MOTHER OF HARLOTS AND OF THE ABOMINATIONS OF THE EARTH.''
6 And I saw the Woman drunk with the blood of the Saints, and with the blood of the witnesses of Jesus. When I saw her, I wondered greatly.

The Angel of God tells the Apostle John not to be amazed; he will explain the mystery to him.  The Beast is none other than the physical embodiment of Satan, the Antichrist, who will end up in destruction or perdition.  Those who will choose to remain unsaved will easily be deceived by the Beast.  The kings of the Earth during the Tribulation Period will follow the Beast into battle against Jesus when He returns in Revelation 19.

7 And the angel said to me, "Why do you wonder? I will tell you the mystery of the Woman and of the Beast that carries her, which has the seven heads and the ten horns."
8 "The Beast that you saw was, and is not, and is about to come up out of the abyss and go to destruction. And those who dwell on the Earth, whose name has not been written in the Book of Life from the foundation of the world, will wonder when they see the Beast, that he was and is not and will come."
9 "Here is the mind which has wisdom. The seven heads are seven mountains on which the Woman sits,"
10 "and they are seven kings; five have fallen, one is, the other has not yet come; and when he comes, he must remain a little while."
11 "The Beast which was and is not, is himself also an eighth and is one of the seven, and he goes to destruction."
12 "The ten horns which you saw are ten kings who have not yet received a kingdom, but they receive authority as kings with the Beast for one hour."
13 "These have one purpose, and they give their power and authority to the Beast."
14 "These will wage war against the Lamb, and the Lamb will overcome them, because He is Lord of Lords and King of Kings, and those who are with Him are the Called and Chosen and Faithful.''
15 And he said to me, "The waters which you saw where the harlot sits, are peoples and multitudes and nations and tongues."
16 "And the ten horns which you saw, and the Beast, these will hate the harlot and will make her desolate and naked, and will eat her flesh and will burn her up with fire."
17 "For God has put it in their hearts to execute His purpose by having a common purpose, and by giving their kingdom to the Beast, until the words of God will be fulfilled."
18 "The Woman whom you saw is the GREAT CITY, which reigns over the kings of the Earth.''

A Second Angel of God comes down from Heaven having great power given to him by God.  He pronounces the crimes of the Harlot:

Jesus now speaks from Heaven, pronouncing the terrible destruction of the Harlot according to the Judgment of God:

4 I heard another voice from Heaven, saying, "Come out of her, My people, so that you will not participate in her sins and receive of her plagues; 
5 for her sins have piled up as high as Heaven, and God has remembered her iniquities.
6 "Pay her back even as she has paid, and give back to her double according to her deeds; in the cup which she has mixed, mix twice as much for her. 
7 "To the degree that she glorified herself and lived sensuously, to the same degree give her torment and mourning; for she says in her heart, "I SIT AS A QUEEN AND I AM NOT A WIDOW, and will never see mourning.'  
8 "For this reason in one day her plagues will come, pestilence and mourning and famine, and she will be burned up with fire; for the Lord God who judges her is strong.  
9 "And the kings of the Earth, who committed acts of immorality and lived sensuously with her, will weep and lament over her when they see the smoke of her burning,  
10 standing at a distance because of the fear of her torment, saying, "Woe, woe, the GREAT CITY, BABYLON, the STRONG CITY! For in one hour your judgment has come.'  
11 "And the merchants of the Earth weep and mourn over her, because no one buys their cargoes any more  
12 cargoes of gold and silver and precious stones and pearls and fine linen and purple and silk and scarlet, and every kind of citron wood and every article of ivory and every article made from very costly wood and bronze and iron and marble,  
13 and cinnamon and spice and incense and perfume and frankincense and wine and olive oil and fine flour and wheat and cattle and sheep, and cargoes of horses and chariots and slaves and human lives.  
14 "The fruit you long for has gone from you, and all things that were luxurious and splendid have passed away from you and men will no longer find them.  
15 "The merchants of these things, who became rich from her, will stand at a distance because of the fear of her torment, weeping and mourning,  
16 saying, "Woe, woe, the GREAT CITY, she who was clothed in fine linen and purple and scarlet, and adorned with gold and precious stones and pearls;  
17 for in one hour such great wealth has been laid waste!' And every shipmaster and every passenger and sailor, and as many as make their living by the sea, stood at a distance,  
18 and were crying out as they saw the smoke of her burning, saying, "What CITY is like the GREAT CITY?'  
19 "And they threw dust on their heads and were crying out, weeping and mourning, saying, "Woe, woe, the GREAT CITY, in which all who had ships at sea became rich by her wealth, for in one hour she has been laid waste!'  
20 "Rejoice over her, O Heaven, and you Saints and Apostles and Prophets, because God has pronounced judgment for you against her.''  

Another Angel of God performs a symbolic act, depicting the destruction of the Harlot and again declaring her guilty of the slaughter of Prophets and Saints of God and everyone else she betrayed:

Again the City of Religious Babylon is revealed, this time by the Apostle Peter, writing from Rome, where a group of Christian believers was located (to these people the Apostle Paul wrote the Book of Romans).  This city is in existence at the time of Peter's writing during the mid-first century A.D.  This was (and is) a current city at Peter's time and is not to be confused with the historical New Testament references (Matthew 1:11, 12, 17, Acts 7:43) to Chaldean Babylon which was located in Shinar, where we find modern-day Iraq:

13 She who is in Babylon, chosen together with you, sends you greetings, and so does my son, Mark.