One of the things people need to know about the Book of Revelation is that most of its imagery and metaphors look like they were pulled directly out of the Old Testament.
The harlot metaphor for "Mystery Babylon" is no exception. If you feel so inclined, do a search for the word "harlot" in the OT, and notice how many times the word is used to describe the idolatry and abominations of both Israel and Judah. But there are two chapters in Ezekiel where this metaphor of the harlot is aimed directly at Jerusalem. First, here are a couple of passages from Revelation for use in comparing to the language in Ezekiel:
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." Revelation 17:1-2 (NASB)
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. Revelation 17:4-6 (NASB)
Now, here are the OT analogs of these verses:
How the faithful city has become a harlot, She who was full of justice! Righteousness once lodged in her, But now murderers. Isaiah 1:21 (NASB)
Then the word of the Lord came to me, saying, 2 "Son of man, make known to Jerusalem her abominations Ezekiel 16:1-2 (NASB)
8 "Then I passed by you and saw you, and behold, you were at the time for love; so I spread My skirt over you and covered your nakedness. I also swore to you and entered into a covenant with you so that you became Mine," declares the Lord GOD. 9 "Then I bathed you with water, washed off your blood from you and anointed you with oil. 10 "I also clothed you with embroidered cloth and put sandals of porpoise skin on your feet; and I wrapped you with fine linen and covered you with silk. 11 "I adorned you with ornaments, put bracelets on your hands and a necklace around your neck. 12 "I also put a ring in your nostril, earrings in your ears and a beautiful crown on your head. 13 "Thus you were adorned with gold and silver, and your dress was of fine linen, silk and embroidered cloth. You ate fine flour, honey and oil; so you were exceedingly beautiful and advanced to royalty. 14 "Then your fame went forth among the nations on account of your beauty, for it was perfect because of My splendor which I bestowed on you," declares the Lord GOD. 15 "But you trusted in your beauty and played the harlot because of your fame, and you poured out your harlotries on every passer-by who might be willing. 16 "You took some of your clothes, made for yourself high places of various colors and played the harlot on them, which should never come about nor happen. Ezekiel 16:8-16 (NASB)
"Behold now, I have stretched out My hand against you and diminished your rations. And I delivered you up to the desire of those who hate you, the daughters of the Philistines, who are ashamed of your lewd conduct. 28 "Moreover, you played the harlot with the Assyrians because you were not satisfied; you played the harlot with them and still were not satisfied. 29 "You also multiplied your harlotry with the land of merchants, Chaldea, yet even with this you were not satisfied."'" 30 "How languishing is your heart," declares the Lord GOD, "while you do all these things, the actions of a bold-faced harlot.
31 "When you built your shrine at the beginning of every street and made your high place in every square, in disdaining money, you were not like a harlot. 32 "You adulteress wife, who takes strangers instead of her husband! 33 "Men give gifts to all harlots, but you give your gifts to all your lovers to bribe them to come to you from every direction for your harlotries. 34 "Thus you are different from those women in your harlotries, in that no one plays the harlot as you do, because you give money and no money is given you; thus you are different."
35 Therefore, O harlot, hear the word of the Lord. 36 Thus says the Lord GOD, "Because your lewdness was poured out and your nakedness uncovered through your harlotries with your lovers and with all your detestable idols, and because of the blood of your sons which you gave to idols, 37 therefore, behold, I will gather all your lovers with whom you took pleasure, even all those whom you loved and all those whom you hated. So I will gather them against you from every direction and expose your nakedness to them that they may see all your nakedness.
38 "Thus I will judge you like women who commit adultery or shed blood are judged; and I will bring on you the blood of wrath and jealousy. 39 "I will also give you into the hands of your lovers, and they will tear down your shrines, demolish your high places, strip you of your clothing, take away your jewels, and will leave you naked and bare. 40 "They will incite a crowd against you and they will stone you and cut you to pieces with their swords. 41 "They will burn your houses with fire and execute judgments on you in the sight of many women. Then I will stop you from playing the harlot, and you will also no longer pay your lovers.
28 "For thus says the Lord GOD, 'Behold, I will give you into the hand of those whom you hate, into the hand of those from whom you were alienated. 29 ~'They will deal with you in hatred, take all your property, and leave you naked and bare. And the nakedness of your harlotries will be uncovered, both your lewdness and your harlotries. 30 ~'These things will be done to you because you have played the harlot with the nations, because you have defiled yourself with their idols. Ezekiel 23:28-30 (NASB)
There can be no question that Mystery Babylon is Jerusalem: judged by God in 70 AD in the same manner by which He judged the city - by the Babylonians - 657 years earlier to the very day, thus bringing an end to the Kingdom of God for them precisely as Christ prophesied.
Hope this helps.