Jerusalem is not Babylon. Rather, the Jerusalem of Revelation so closely resembled the Babylon of Jeremiah that it was referred to as Babylon (also Egypt and Sodom) as a warning. Read Jeremiah 50 and 51 before reading Revelation. Then consider Matt 16:23 with regards to whom Jesus was speaking, and how He addressed him.
Jer 51:13 O thou that dwellest upon many waters, abundant in treasures, thine end is come, and the measure of thy covetousness.
Rev 17:1 And there came one of the seven angels which had the seven vials, and talked with me, saying unto me, Come hither; I will shew unto thee the judgment of the great whore that sitteth upon many waters: