New Defender's Study Bible Notes
16:19 cities of the nations. The destructive force of this global earthquake will be so great that, like Jericho at the shout of Joshua’s army, “the cities of the nations fell,” meaning that all their structures collapsed. Jerusalem, however, will not fall, but God will divide it through the midst of the Mount of Olives (the Valley of Kidron already divides it into two parts—note Zechariah 14:4,8) when the Lord returns to stand on the Mount of Olives. Other Old Testament prophets also foresaw this mighty earthquake (e.g., Haggai 2:6-7; Isaiah 24:17-21; Joel 3:16).
16:19 Babylon. The destruction of Babylon had also been noted in Revelation 14:8, but this particular theme is so important that John will interrupt the chronological account at this point in order to devote two entire chapters (Revelation 17 and 18) to it.