Not saying that anyone is right or wrong, but consider this. just follow the theme “great city” one will find their answer who this Mystery Babylon is
Revelation 14:8 "And there followed another angel, saying, Babylon is fallen, is fallen, that great city, because she made all nations drink of the wine of the wrath of her fornication.
Revelation 17:14-18 "These shall make war with the Lamb, and the Lamb shall overcome them: for he is Lord of lords, and King of kings: and they that are with him are called, and chosen, and faithful. And he saith unto me, The waters which thou sawest, where the whore sitteth, are peoples, and multitudes, and nations, and tongues. And the ten horns which thou sawest upon the beast, these shall hate the whore, and shall make her desolate and naked, and shall eat her flesh, and burn her with fire. For God hath put in their hearts to fulfil his will, and to agree, and give their kingdom unto the beast, until the words of God shall be fulfilled. now verse 18 "And the woman which thou sawest is that great city, which reigneth over the kings of the earth".
the key to all these verse is at verse 3 at the start of this chapter. listen, Revelation 17:3 "So he carried me away in the spirit into the wilderness: and I saw a woman sit upon a scarlet coloured beast, full of names of blasphemy, having seven heads and ten horns".
please take note, John was in spirit in the "wilderness". this is very important.
so the woman is that "GREAT CITY", so let's follow this great city
Revelation 18:10 "Standing afar off for the fear of her torment, saying, Alas, alas, that great city Babylon, that mighty city! for in one hour is thy judgment come.
Revelation 18:16 "And saying, Alas, alas, that great city, that was clothed in fine linen, and purple, and scarlet, and decked with gold, and precious stones, and pearls!
Revelation 18:19 "And they cast dust on their heads, and cried, weeping and wailing, saying, Alas, alas, that great city, wherein were made rich all that had ships in the sea by reason of her costliness! for in one hour is she made desolate.
Revelation 18:21 "And a mighty angel took up a stone like a great millstone, and cast it into the sea, saying, Thus with violence shall that great city Babylon be thrown down, and shall be found no more at all.
Revelation 21:10 "And he carried me away in the spirit to a great and high mountain, and shewed me that great city, the holy Jerusalem, descending out of heaven from God,
STOP, how can holy Jerusalem be that GREAT CITY. it's not, and here's why, Revelation 21:10a "And he carried me away in the spirit", to a great and high mountain. not in the wilderness as in Revelation 17:3 "So he carried me away in the spirit into the wilderness: and I saw a woman sit upon a scarlet coloured beast, full of names of blasphemy, having seven heads and ten horns", it not SPIRITUAL JERUSALEM, but NATURAL JERUSALEM. let's get the meat . the Church is a Woman who fell in apostasy, other wise known as the "GREAT" falling away, hence the title the "GREAT" city. 2 Thessalonians 2:3 "Let no man deceive you by any means: for that day shall not come, except there come a falling away first, and that man of sin be revealed, the son of perdition" hence the call to come out of her. Revelation 18:4 "And I heard another voice from heaven, saying, Come out of her, my people, that ye be not partakers of her sins, and that ye receive not of her plagues". the term MY PEOPLE is constant theme used by God himself. only a rennet will be saved. I believe the Prophet Isaiah make reference to this coming out. Isaiah 52:9-11 "Break forth into joy, sing together, ye waste places of Jerusalem: for the LORD hath comforted his people, he hath redeemed Jerusalem. The LORD hath made bare his holy arm in the eyes of all the nations; (this is reference to the Lord Jesus), and all the ends of the earth shall see the salvation of our God. Depart ye, depart ye, go ye out from thence, touch no unclean thing; go ye out of the midst of her; be ye clean, that bear the vessels of the LORD". here the vessel is reference to the temple of God our BODIES. scripture, 1 Corinthians 6:19 "What? know ye not that your body is the temple of the Holy Ghost which is in you, which ye have of God, and ye are not your own?". this to me certify, 2 Thessalonians 2:3 "Let no man deceive you by any means: for that day shall not come, except there come a falling away first, and that man of sin be revealed, the son of perdition Who opposeth and exalteth himself above all that is called God, or that is worshipped; so that he as God sitteth in the temple of God, shewing himself that he is God".
Now the final revelation which shows that the woman, the "great city" is natural Jerusalem
Revelation 11:8 "And their dead bodies shall lie in the street of the great city, which spiritually is called Sodom and Egypt, where also our Lord was crucified". here that great city is none other than Jerusalem.
this is my understanding of Mystrey Babylon