I said in our last study that Babylon isn't to be interpreted as any one actual city or location. I believe it is a symbolic picture of the world's system that lures mankind into immorality and idolatry. Babylon, throughout the Old Testament became symbolic for the ultimate enemy of the people of God. John picks up this theme to describe the world's system, designed not only to persecute God's people, but to entice and lure them into sin.
So we've seen John describe antichrist and the political structures organized against devotion to Christ. Then we saw the beast and the construction of worship structures organizes against devotion to Christ. And now John sees Babylon, representing the enticement structures of this world constructed to pull people into an easy tolerance and enjoyment of things displeasing to God.
Remember, these visions are first given to John and a people with centuries of Old Testament background and study. Babylon is the ultimate picture of everything that held Israel captive for so long in idolatry and judgment.