“It shall be more tolerable for the land of Sodom and Gomorrah in the day of judgment than for that city.”
These words spoken by Jesus Christ Himself are contained in the Gospel of Saint Matthew (10:15).
And the first thing to be deduced from them is that Jesus Christ recognizes what was suffered by the two cities as real punishment and, therefore, the depravities committed by those two cities as true sins, wherefore both suffered the wrath of God in the form of fire falling from heaven that reduced them to ashes. The full particulars of this event are described in the complete narrative provided by chapters 18 and 19 of the Book of Genesis.
But the words of Christ were spoken to men of all times and in all places. Hence we may infer, with complete certainty, that the same punishment will be applied to any city that is in the same circumstances. Next, we should ask ourselves to which city Jesus Christ might be referring that is to be treated even more severely than Sodom and Gomorrah. These famous words of Saint Augustine may help us: Two cities have been formed by two loves: the earthly by the love of self, even to the contempt of God; the City of God by the love of God, even to the contempt of self (Saint Augustine, The City of God, Book 14, Chapter 28).