Revelation 17:18
Verse eighteen: “And the woman which thou sawest is that great city, which reigneth over the kings of the earth”
The woman is Babylon.
The full title o the woman is "Babylon the Great, the Mother of Prostitutes and Abominations of the Earth." This definition represents the deeds of Babylon against mankind during the tribulation.
For context see Revelation 17:1–15 & 18
Babylon represents the commercial and religious system of Rome back in antiquity, it is reborn during the tribulation as the one world government and monetary system of the Anti Christ as the mark of the beast. It is a physical location where the remaining population will be driven to where all trade and commerce will take place during the tribulation. (Revelation 18)