Fallen, Fallen is Babylon the Great: The City of Man Will Fall

Proposition: This current age is marked by two cities that have two different loves. The City of Man loves itself and loves the world and is doomed to destruction. So those belonging to the City of God must be careful not to be found loving the things of this world.
Who is the Great Prostitute, Babylon the Great?
What is the end of the City of Man and its loves?
What should the citizens of the City of God do?