The only viable identification remaining is the conclusion already reached; it is Babylon on the Euphrates. The OT prophecies of Babylon’s destruction in Isaiah 13 and Jeremiah 51 are yet unfulfilled and are awaiting the future Day of the Lord for that fulfillment (Isaiah 13.6) (Seiss). Furthermore, Babylon on the Euphrates has a location that fits this description politically, geographically, and in all the qualities of accessibility, commercial facilities, remoteness of interferences of church and state, and yet centrality in regard to the trade of the whole world (Seiss).
In the future day anticipated in the pages of this prophecy, this city will become the focal point for a religious system staunchly opposed to the truth of Christianity. The system will thrive, for a time, in gaining influence over the commercial and political entities of its time, until the beast and the ten kings determine that it no longer has a usefulness for their purposes. They will then dismantle it.
From: Revelation 8-22: An Exegetical Commentary by Robert L. Thomas (Chicago: Moody Press, 1995), pp. 307-308 (from the exposition of Revelation 17.18). The commentary exegetes the Book of Revelation from the point of view of conservative premillennial dispensationalism.