Where or what is Babylon as described in Book of Revelation?

A question for Christians and/or any individual who will respond sincerely as this a weighty topic for sure. Do you believe the Babylon referred to in the Book of Revelation (and some Old Testament bible books) is a geographic place and if so, which one, or do you believe it symbolizes the greed of the world’s economic system? Do you know of any books or internet threads that seriously comment on this and can support it well?