There are actual several variations of the argument, but it boils down to an anti-Catholic interpretation of Revelation chapter 17 which describes Babylon the Great, the Great Harlot (whore) who sits upon many waters (nations, tribes, peoples, and tongues) and who also sits upon seven hills. The argument claims that this points to the Roman Catholic church since we encompass people of all races and languages and also because Rome, from whence the Pope reigns, is a city which sits on seven hills. That’s basically it. Of course, it’s nonsense, even if only for the fact that Vatican Hill (where St. Peter’s basilica is) is not even one of
the Seven Hills of Rome !!
Love, Jaypeeto3