The question is, how different from the Babylon of chapter 17 is the Babylon of chapter 18? Undoubtedly the city is the same in both instances. Both have the name Babylon the great (Rev. Rev. 17:5+; Rev. 18:2+). Both are guilty of fornication (Rev. Rev. 17:1+, Rev. 17:2+, Rev. 17:4+, Rev. 17:5+, Rev. 17:16+; Rev. 18:3+) and of causing the kings of the earth and the earth-dwellers to imbibe of the wine (of the anger) of the citys fornication (Rev. Rev. 17:2+; Rev. 18:3+). The destiny of both is to be burned with fire (Rev. Rev. 17:16+; Rev. 18:8+, Rev. 18:9+, Rev. 18:18+) and to become an utter desolation (Rev. Rev. 17:16+; Rev. 18:17+, Rev. 18:19+). In both chapters Babylon is the great city (Rev. Rev. 17:18+; Rev. 18:10+, Rev. 18:16+, Rev. 18:18+. 19, 21) and wears the apparel and adornment of a harlot (Rev. Rev. 17:4+; Rev. 18:16+). Both are responsible for the martyrdom of the faithful (Rev. Rev. 17:6+; Rev. 18:20+, Rev. 18:24+ [cf. Rev. 19:2+]).2
If we look at these two chapters carefully [Rev. Rev. 17:1+ and Rev. 18:1+], we fail to find the distinction so persistently affirmed. Some one states a thing as a fact; and then others think they see it. There is no such thing as Mystic Babylon. The Babylon mentioned in chapter Rev. 17:1+ is the same as that in chapter Rev. 18:1+. It is the Woman which is a secret symbol or sign. But that means only that we are not to take it literally as a woman, but as that great city, as is explained in [Rev. Rev. 17:18+].4
1 A strong exegetical case can be made to support the proposition that Revelation Rev. 17:1+ and Rev. 18:1+ should be viewed as a unit speaking of one Babylon rather than two separate units speaking of two Babylons. The notion of viewing Revelation Rev. 17:1+ and Rev. 18:1+ as a unit is buttressed by noting the similarities between the chapters. Both chapters refer to Babylon as having the same name (Rev. Rev. 17:5+; Rev. 18:2+), holding a cup (Rev. Rev. 17:4+; Rev. 18:6+), fornicating with kings (Rev. Rev. 17:2+; Rev. 18:3+), being drunk with the wine of immorality (Rev. Rev. 17:2+; Rev. 18:3+), persecuting believers (Rev. Rev. 17:6+; Rev. 18:24+), experiencing destruction by fire (Rev. Rev. 17:16+; Rev. 18:8+), and experiencing destruction by God (Rev. Rev. 17:17+; Rev. 18:5+, Rev. 18:8+).Andy Woods, What is the Identity of Babylon In Revelation 17-18?.