Seven Vial Plagues
The Father; no one else can be in the temple.
The "vials of the wrath of God" is a description of what the vials are, not the Father referring to himself in the third person. This titling acts much like "the supper of the great God" in 19:17.
"Your ways" is supplied in translation; the Greek reads ὑπάγετε καὶ ἐκχέετε — "Go and pour out."
Re 15:1, Re 16:1 — Seven messengers with the last seven plagues.
The First Vial: Earth Sores
Important Note: The text here takes an immediate turn from the application of the plagues in the Trumpets, where we saw those who "have not the seal of God in their foreheads," and this time, those "which had the mark of the beast" are noted. This seems to signal a pivot in who is on earth: "the 144,000 are no longer on Earth as they were at the 5th trumpet, so we must identify people by the mark of the beast; the seal of God is not applicable any longer. The 144,000 have been reaped." And the fact that its identification is specifically at the time of the first vial should also tell us something; the text really feels to be driving that point and knows it needs to do so at the first vial.
The second "upon" is not repeated in the critical text: one preposition governs both groups, ἐπὶ τοὺς ἀνθρώπους … καὶ τοὺς προσκυνοῦντας.
Re 8:7, Re 16:2 — The larger point is that the trumpet and vial plagues both affect the whole earth. That is why they often feel similar. It is not necessarily because they are retelling the same story from a different angle or perspective.
Re 9:5, Re 16:2 — Revelation 9:5 and 16:2 may suggest a connection between the mark of the beast and the locusts in Revelation 9, as both relate to pain rather than explicit death. This does not mean the first woe occurs at the same time as the first bowl. Both passages involve a marked or sealed distinction. In Revelation 9, the mark of the beast is not yet mentioned; instead, the locusts are permitted to harm only those who do not have the seal of God on their foreheads. This absence should be noticed, though it should be handled carefully. The text does not explicitly say the mark is not present yet; it simply has not introduced it here.
By Revelation 16:2, however, after what appears to be the reaping of the saints, the text speaks directly of those who have “the mark of the beast” and who worship his image. Both passages also involve painful harm rather than immediate death: Revelation 9 describes torment like the sting of a scorpion, while Revelation 16 describes a loathsome and malignant sore on those who have the mark of the beast. This may suggest that Revelation 9 prepares for, or is connected to, the later mark-of-the-beast judgment, without requiring the first woe and first bowl to be the same event.
Re 9:4, Re 16:2 — Seal of God to mark of beast pivot. In Rev 9:4, the 144,000 appear to be present, and in Rev 16:2, they are not because the mark of the beast is the identifiable mark.
The Second Vial: Sea to Blood
The KJV/TR reads "the second angel"; the critical text reads ὁ δεύτερος — "the second" — alone, as in each vial from here to the seventh.
Unless otherwise indicated, life translates ζωή (zōē), denoting life as possessed or imparted. Lifeᵖ translates ψυχή (psychē), denoting the living self, person, or one’s personal life. The superscript p is an editorial marker for psychē and is not part of the Greek text.
Re 8:8, Re 16:3 — The larger point is that the trumpet and vial plagues both affect the whole earth. That is why they often feel similar. It is not necessarily because they are retelling the same story from a different angle or perspective.
The Third Vial: Fresh Water to Blood
The KJV/TR reads "the third angel"; the critical text reads ὁ τρίτος — "the third" — alone.
Re 8:10, Re 16:4 — The larger point is that the trumpet and vial plagues both affect the whole earth. That is why they often feel similar. It is not necessarily because they are retelling the same story from a different angle or perspective.
The KJV's "and shalt be" follows Beza's TR, ὁ ἐσόμενος; Stephanus 1550 instead reads καὶ ὁ ὅσιος — "and the Holy One" — where the critical text has ὁ ὅσιος without the conjunction. Both TR editions also include Κύριε — "O Lord" — which the critical text lacks. As at 11:17, the title stops at "who is and who was" once the reign has begun and the judgments are underway.
The KJV/TR includes γάρ — "for they are worthy"; the critical text reads ἄξιοί εἰσιν — "they are worthy" — without it.
It's not clear which voice is the one from the altar: the altar itself, or one by it, over it, or under it.
The KJV/TR reads "I heard another out of the altar say"; the critical text reads ἤκουσα τοῦ θυσιαστηρίου λέγοντος — "I heard the altar saying."
Re 6:9, Re 16:7 — If sounds are coming from the altar, or it is speaking, then it is likely that those under it are still, not yet resurrected.
Re 9:13, Re 16:7
The Fourth Vial: Scorching Sun of Heaven
The KJV/TR reads "the fourth angel"; the critical text reads ὁ τέταρτος — "the fourth" — alone.
Re 16:8, Re 19:17 — Soft connection.
Re 7:16, Re 16:9 — This seems to agree that the church is not touched by this heat.
The Fifth Vial: Pain of Darkness
The KJV/TR reads "the fifth angel"; the critical text reads ὁ πέμπτος — "the fifth" — alone.
Re 13:1-7, Re 13:12, Re 13:14-15, Re 13:16, Re 16:10, Re 16:13, Re 19:19-20, Re 20:10 — The sea beast, not the red dragon. In Revelation 16:13 the beast is distinct from the dragon.
Re 9:2, Re 16:10 — Darkness is a theme of Revelation. This theme is connected to the "day of the Lord" and does not imply that these events are the same. They mainly display the characteristics of the day of the Lord.
The Sixth Vial: Gathering of Kings by Unclean Spirits
Important Note: Genesis 15:18 says, "In the same day the Lord made a covenant with Abram, saying, Unto thy seed have I given this land, from the river of Egypt unto the great river, the river Euphrates," so it seems God is removing the boundary line of the covenant land to judge the kings in His people's land. Further, there is an image here of those in Genesis 10:10, "And the beginning of his kingdom was Babel, and Erech, and Accad, and Calneh, in the land of Shinar." And then, speaking of Shinar/Babylon, Genesis 11:2 says, "And it came to pass, as they journeyed from the east, that they found a plain in the land of Shinar; and they dwelt there." So, it might be the intent of the text that the eastern (rising sun) kings of Babylon cross the boundary line into the promised land, and God will judge them there.
“The rising” (ἀνατολή) is the common Greek expression for “east,” taken from the place of the sun’s rising. Hence “from the rising of the sun” (ἀπὸ ἀνατολῆς ἡλίου) is but a fuller and more literal form of saying “from the east.”
The KJV/TR reads "the sixth angel"; the critical text reads ὁ ἕκτος — "the sixth" — alone.
Re 9:14, Re 16:12, Isaiah 8:7-8 — The Old Testament background of the Euphrates strengthens the connection between Revelation 9:14 and 16:12, but it does not require the two passages to describe the same event. In the Old Testament, the Euphrates is the great boundary river of the promised land, the edge of Israel’s dominion, and the direction from which hostile imperial powers such as Assyria and Babylon are associated. Isaiah 8:7-8 even uses the waters of the Euphrates as an image of Assyria’s invading power overflowing the land.
Therefore, when Revelation returns to “the great river Euphrates,” the imagery is not random. The river evokes boundary, empire, invasion, and judgment. In Revelation 9:14, the Euphrates is the place where bound destructive powers are released. In Revelation 16:12, the Euphrates is dried up so the way is prepared for the kings from the east. These passages share an Old Testament judgment setting, but their actions are distinct. The shared Euphrates imagery points to a common theme of whole-earth judgment and war, not necessarily to a one-to-one retelling of the same plague.
Re 16:13, Re 16:14
Re 11:7, Re 16:13 — 16:13 is the place where the sea beast is referred to simply as "the beast," since the other figures are identified by name: the dragon, the beast, and the false prophet. This makes it most likely that "the beast" in 11:7 refers to the sea beast. If so, it also connects the sea beast with the ascent from the bottomless pit, even though the text does not explicitly describe him as emerging from the pit by means of the key, as it does in the other passages.
For the "great day" in Revelation 6, we might be tempted to link this verse to that time. It would be a mistake to think of "the great day" as a 24-hour day. This "great day" is designated, not counted — it follows Revelation's article-noun-article-adjective pattern for the book's major entities (compare the great city, the great river, the great winepress, and the tribulation, the great one in 7:14). Revelation 6 shows the day's dawn: the kings of the earth announce its arrival — "the great day of their wrath is come" (6:17) — as God interrupts the beast's peak. What is not yet at that point is the day's climax: the war of the great day, whose gathering comes at this vial and whose battle the rider fights when the narrative resumes — "the war," with the article (19:19), pointing back to this verse. The day runs from its dawn at the 6th seal to the 7th-vial complex and its war — designated from end to end, never counted.
The KJV/TR reads "the kings of the earth and of the whole world"; the critical text reads τοὺς βασιλεῖς τῆς οἰκουμένης ὅλης — "the kings of the whole world."
Re 16:13, Re 16:14
Re 16:14, Re 16:16, Re 19:17, Re 19:19, Re 20:8 — While “gathering” is set in the context of war in Revelation, this does not mean that all gatherings are the same event. The war gatherings in Revelation 16 and 19 are both connected with the winepress imagery, but the war in Revelation 20 is not.
Further, the war in Revelation 20 is waged by Satan himself, while the wars in Revelation 16 and 19 are associated with the beast and the false prophet. Revelation 20 takes place only after Satan is released from the bottomless pit. Revelation 20:10 also makes clear that the beast and the false prophet are already in the lake of fire before this final war is completed.
This order matters. Revelation 19 shows the beast and the false prophet being cast into the lake of fire, and only afterward is Satan bound and cast into the bottomless pit. Therefore, the war of Revelation 20 should not be collapsed into the war gatherings of Revelation 16 and 19 simply because the word or theme of “gathering” appears in each context. The Greek adds its own precision here. The beast's and the dragon's earlier wars are made without the article — ποιήσει πόλεμον (11:7), ποιῆσαι πόλεμον (12:17; 13:7) — but at 19:19 the make-war phrase uniquely takes it: ποιῆσαι τὸν πόλεμον, "to make the war," pointing back to the war already tagged at 16:14 as "the war of the great day of God, the Almighty." Revelation 20:8 also reads εἰς τὸν πόλεμον, the same gathering construction as 16:14, but without 16:14's genitive tag: its article designates that episode's own appointed war, a thousand years later, not the tagged war of the great day. (The critical text carries these articles; the KJV reads "the battle of that great day" at 16:14, following the TR's demonstrative, and "to battle" at 20:8.)
Re 6:17, Re 16:14 — The phrase “the great day” appears explicitly in Revelation 6:17 and 16:14. In 6:17, it is spoken by the nations in fear as they perceive the onset of divine wrath, "the great day of their wrath is come," whereas in 16:14 John uses it narratively to describe the gathering for its climactic outworking, "to gather them (the kings of the earth) to the war of the great day". This suggests not a mere looming concept in the minds of the nations throughout the book, but a thematic thread that begins with human recognition of impending judgment (6:17) and culminates in the final confrontation orchestrated by God (16:14 onward). The day appears to run from the 6th seal to the 7th vial: at the 6th seal it dawns, and at the 7th-vial complex it ends in the war the rider fights (19:19, "the war," with the article pointing back to 16:14). And it carries no count — like "the hour of testing" (3:10) and the hour to reap (14:15), it designates an appointment, not a length, so its span need not be 24 hours.
I Come as a Thief
Important Note: In 1 Thessalonians 5:4, Paul writes, “But you, brethren, are not in darkness, that the day would overtake you like a thief” (NASB95). In that passage, the subject is “that day,” referring back to “the day of the Lord” in 1 Thessalonians 5:2. However, in Revelation 16:15, Jesus says, “Behold, I am coming like a thief” (NASB95). Here, the thief imagery is applied directly to Jesus’ own coming, not to “the day.” This suggests that Revelation 16:15 shares the same typological warning of suddenness and watchfulness found in 1 Thessalonians 5, but the two passages should not be treated as strictly synonymous. In 1 Thessalonians 5, the day comes like a thief; in Revelation 16:15, Jesus Himself comes like a thief.
Sardis: Church 5
The phrase "he who watches" is connected to Sardis' call to "be watchful" and to Jesus' reminder that he is coming like a thief.
Laodicea: Church 7
The phrase "keeps his garments" is connected to the garments washed in the blood of the Lamb and pointed at Laodicea. We see this connection in 3:18 in the same context but with expanded meaning: "buy from Me gold refined by fire... white garments so that you may clothe yourself". The nakedness here appears to be not that of the flesh but of personhood.
Two things should be said together here. One: this verse is not addressing anyone inside the narrative as part of the scene — it does not place saints in the context of the plagues. The scene's own narration runs in the third person (16:13-14, 16), and this verse breaks the frame with Jesus' own first-person voice, exactly as in 22:7. It speaks the language of the seven letters — "watch... I come as a thief" is Sardis (3:3), and "keepeth his garments, lest he walk naked, and they see his shame" is Laodicea (3:18) — and it is the third of the book's seven blessings (1:3; 14:13; 16:15; 19:9; 20:6; 22:7; 22:14), a series spoken to the reader in every instance: "Blessed is he that readeth" (1:3), "Blessed is he that keepeth the sayings of the prophecy of this book" (22:7).
Two: the text is talking to the reader — and its placement pulls that reader into this moment. This is not only an abstract warning. Positioned between the gathering (16:14) and Har-Magedon (16:16), it stands as a warning to whoever is in that moment when it unfolds, reading the words as they come to pass. And there will be someone to warn. The seal-to-mark pivot at the first vial (16:2) shows the sealed are gone, but the hour of testing was designated "to try them that dwell upon the earth" (3:10), and a test implies the possibility of passing it. The refrain "repented not" (16:9, 11) records the response of the plagued, not the closing of the door — the witnesses' earthquake already showed a remnant giving glory to God under judgment (11:13). This may be grace on display: chance upon chance to repent, from the reaping to the white horse. It may even be that God, in mercy, removes those who believe at the right time in order to display His goodness to those who still need to repent — goodness meant to lead them to repentance (Romans 2:4). The human desire is for a clean, uninterrupted story with no bumps in the road; too much texture feels wrong. But maybe more is going on than a single clean line — and that is okay. Until Jesus comes on the white horse, time is not up for everyone — and even then, a thousand years of story remain.
The verse is also a marker for the reader: at the sixth vial the coming is still "I come" — future. The white horse has not yet come; the reaping is already past. And note which thief-coming this is: Jesus Himself comes as a thief here, as in 3:3 — not the same statement as the day of the Lord coming as a thief (1 Thessalonians 5:2; 2 Peter 3:10).
Re 3:3, Re 16:15 — Keep in mind this is an idiom for a time that is not expected.
Re 16:15, Re 19:11
Har-Magedon is a debated location: Megiddo or Mount Zion.
If Har-Magedon is understood as “Megiddo,” a difficulty arises, since Megiddo itself is not a mountain but a tell (an elevated mound) situated in the Jezreel Valley. There is no place in Scripture where הַר (har) is clearly and explicitly used for an archaeological mound such as this.
While har most often denotes a mountain, it can also refer more broadly to hill country or a regional highland rather than a single peak (Joshua 17:15; Judges 2:9; 1 Kings 20:23). However, it is not naturally applied to a site like Megiddo in the biblical record.
For this reason, the expression “mountain of Megiddo” is not a straightforward geographical designation. It could be argued that Megiddo might become a literal mountain in the future, but this would be a stretch, as the text appears to present the name as something intelligible to its original audience rather than a wholly future geographical transformation.
Megiddo is consistently associated with decisive conflict and national tragedy—most notably the death of Josiah (2 Kings 23:28–30; 2 Chronicles 35:20–25), later echoed in the imagery of great mourning (Zechariah 12:11). Thus, the term may carry symbolic or theological weight rather than strict topographical precision. At the same time, any attempt to define it as a specific “spiritual name” (e.g., a direct identification with Jerusalem or Mount Zion) moves beyond what the text itself explicitly supports and should be held with interpretive caution.
Some scholars read Har-Magedon here as "Mount Zion," which is possible, as we see in 16:19, "the great city" (11:8, 16:19) is divided into three parts. Under the Critical Text, "great city" language in Revelation is tied to spiritually rebellious city imagery: Jerusalem is called the great city in 11:8, spiritually Sodom and Egypt, while Babylon is called the great city in 17:18 and throughout chapter 18. This does not require flattening Jerusalem and Mystery Babylon into the same object, but it does show that Revelation can use city language theologically and typologically.
If Mystery Babylon in Revelation 17 is this Jerusalem where the kings gather here to burn her with fire and she is completely removed and seen no more at all by the 10 kings, as 17 makes clear, then how does Jesus come to the mountain to fight them in a place completely removed? The simple answer is that Mystery Babylon is not the same place we are reading about the kings gathering to.
This study suggests that the beast and kings are gathered together in this place (Jerusalem), well after the fall of Mystery Babylon. They gather in 16:14 to fight against the Lord of Lords, and he will overcome them. If Jerusalem is the symbol of Jesus' rightful land, these kings seem to gather to war with Jesus over it.
Re 16:14, Re 16:16, Re 19:17, Re 19:19, Re 20:8 — While “gathering” is set in the context of war in Revelation, this does not mean that all gatherings are the same event. The war gatherings in Revelation 16 and 19 are both connected with the winepress imagery, but the war in Revelation 20 is not.
Further, the war in Revelation 20 is waged by Satan himself, while the wars in Revelation 16 and 19 are associated with the beast and the false prophet. Revelation 20 takes place only after Satan is released from the bottomless pit. Revelation 20:10 also makes clear that the beast and the false prophet are already in the lake of fire before this final war is completed.
This order matters. Revelation 19 shows the beast and the false prophet being cast into the lake of fire, and only afterward is Satan bound and cast into the bottomless pit. Therefore, the war of Revelation 20 should not be collapsed into the war gatherings of Revelation 16 and 19 simply because the word or theme of “gathering” appears in each context. The Greek adds its own precision here. The beast's and the dragon's earlier wars are made without the article — ποιήσει πόλεμον (11:7), ποιῆσαι πόλεμον (12:17; 13:7) — but at 19:19 the make-war phrase uniquely takes it: ποιῆσαι τὸν πόλεμον, "to make the war," pointing back to the war already tagged at 16:14 as "the war of the great day of God, the Almighty." Revelation 20:8 also reads εἰς τὸν πόλεμον, the same gathering construction as 16:14, but without 16:14's genitive tag: its article designates that episode's own appointed war, a thousand years later, not the tagged war of the great day. (The critical text carries these articles; the KJV reads "the battle of that great day" at 16:14, following the TR's demonstrative, and "to battle" at 20:8.)
The Seventh Vial: Voices, Thunders, Lightnings, & Earthquake
Important Note: We know this version of "the great city" (16:19) is very likely Jerusalem. The first time we encounter "great city" is in Jerusalem in 11:8. Jerusalem held the title of "great city" until 16:19. When we see "great city" applied again, it is to Mystery Babylon in Revelation 17. However, when Mystery Babylon falls, the cities of the nations are still standing and lament her fall. Here in 16:19, all the cities have fallen, which suggests none are left to mourn for the "great city" in 16:19.
Also, speaking of Mystery Babylon, Revelation 18 uses the same phrase as Revelation 14:8: "is fallen, is fallen." Revelation 14 places that fall before the warning about the mark of the Beast and before the patience of the saints in 14:9-12, which points to the Beast-period crisis rather than the final vial. Revelation 14 also warns that wrath is still coming, while Revelation 16:19 presents the final vial where that wrath has reached its close. This places Mystery Babylon of Revelation 17-18 earlier in the timeline. And by Revelation 18, Mystery Babylon is gone forever and shall be found no more at all. Here in 16:19, the "great city" falls after the temple in heaven is closed, and none can enter.
At the same time, Revelation 16:19 also says that "great Babylon came in remembrance before God." That phrase should not be ignored. It shows that this judgment belongs to the larger Babylonian pattern of rebellion, city-power, and divine wrath. So this study reads 16:19 as Jerusalem in location, Babylonian in category, and still distinct from Mystery Babylon as the woman riding the beast.
Further, Jesus judges this “great city” directly in the winepress of wrath. Mystery Babylon, however, is judged by the ten kings through God's authority. Mystery Babylon "shall be found no more at all" in a physical sense, not allegorical, but the “great city” in 16:19 is only divided into three parts. Numerous other differences make it very hard to justify Jerusalem as Mystery Babylon without many paradoxes or contradictions.
The Father is the only one in the temple still; none can enter until all the vials are poured out, and its events are not finished until 16:21.
The KJV/TR reads "the temple of heaven"; the critical text reads ἐκ τοῦ ναοῦ, ἀπὸ τοῦ θρόνου — "out of the temple, from the throne" — without "of heaven." The verse's "angel" is likewise a TR plus: the critical text reads ὁ ἕβδομος — "the seventh" — alone.
Re 16:17, Re 21:6
The phrase "of such magnitude an earthquake, so great" declares twice that the earthquake is great by "magnitude/mighty" and "so great." In Greek, this is "τηλικοῦτος σεισμὸς οὕτως μέγας" (NA28), intensifying the description beyond the simple adjective μέγας (“great”). The term τηλικοῦτος (tēlikoutos) denotes “of such magnitude” or “so great in extent,” functioning as a demonstrative of degree rather than a synonym for greatness itself. Thus, the construction is deliberately emphatic, yielding a hyper-literal sense: “an earthquake of such magnitude, so great.” The repetition is rhetorical, underscoring the event's unparalleled nature rather than introducing a new descriptive category. This is important because we see a great earthquake (σεισμὸς μέγας) in many places, such as the 6th seal, but none of them is as distinguished as the earthquake in 16:18.
This story about the winepress will pick back up in 19:15. The parenthetical about Mystery Babylon and the wedding supper of the Lamb will interrupt the story about "the wine of the fierceness of his wrath".
When the text says "great Babylon came in remembrance before God", it should not be ignored or treated as a throwaway phrase. It marks the judgment of this "great city" as belonging to the larger Babylonian pattern of rebellion. That does not require the divided city of 16:19 to be identical in every respect to the woman-city of Revelation 17-18. Revelation 18 echoes Revelation 14:8 with the phrase "is fallen, is fallen," and Revelation 14 places that fall before the mark warning and before the promised wrath is poured out. By Revelation 16:19, the final vial has arrived and that wrath has come to its close.
Re 11:8, Re 14:20, Re 16:19 — This "great city" (Revelation 16:19) is very likely Jerusalem in location. The Old Testament Babylon texts concern the same city and region of Babel/Babylon in Shinar across more than one historical phase: Babel in Shinar (Genesis 10:10; 11:2), the Chaldean Babylon of Nebuchadnezzar (Daniel 4:30), and Babylon's overthrow involving the Medes (Isaiah 13:17-20). Isaiah's comparison, "as when God overthrew Sodom and Gomorrah" (Isaiah 13:19), is about Babylon; it does not make Sodom, Egypt, Jerusalem, or other judged cities into places directly called Babylon.
Revelation 11:8 separately shows that Jerusalem can receive spiritual names, since it is called Sodom and Egypt where the Lord was crucified. This also gives Jerusalem a known location: we know where Jesus was crucified, so Jerusalem is not a mystery in location. Revelation 17 then introduces Mystery Babylon as a woman-city whose location is not named. Do not confuse Jerusalem, where the sea beast appears to rule, with Mystery Babylon as the woman-city. At the same time, Revelation 16:19 says "great Babylon" came in remembrance before God, so Jerusalem under beastly rule may still be judged in relation to the Babylonian pattern without being identical to Mystery Babylon.
Re 11:8, Re 16:19, Re 17:18, Re 18:10, Re 18:16, Re 18:18, Re 18:19 — The phrase "the great city" (ἡ πόλις ἡ μεγάλη) appears to function as a theologically loaded designation in Revelation, used predominantly for Babylon (Rev 17:18, 18:10, 18:16, 18:18, 18:19), yet applied to Jerusalem in Revelation 11:8—"where also our Lord was crucified." In that context, Jerusalem is "spiritually" called Sodom and Egypt, indicating a transformation from its identity as the "holy city" (Rev 11:2) into one aligned with paradigmatic centers of rebellion and judgment. This suggests that Revelation is not using the term merely geographically, but associating it with a city's spiritual condition and opposition to God.
Because Revelation 17:18 defines "the great city" as the one that "reigneth over the kings of the earth," it may be inferred that the designation corresponds to a center of dominant, God-opposing power. When read alongside Revelation 11:8, this raises the possibility that Jerusalem, in its corrupted state and in connection with the rise of the beast, temporarily participates in that same category (It is possible to infer from Daniel 11:45 and 2 Thessalonians 2:4 that Jerusalem becomes a focal point of the final ruler's activity). However, while this pattern allows for a typological relationship—because Babylon is "the great city"—the text does not explicitly state that the title transfers sequentially or that Jerusalem becomes identical with "Mystery Babylon." Thus, "the great city" may function as a theological marker for a ruling, rebellious center.
As for Revelation 16:19, also marked as "the great city," it does not automatically become Jerusalem or Mystery Babylon; such a claim must remain a reasoned inference drawn from the book's patterned language rather than an explicit textual claim. But because we know Mystery Babylon is the only other "great city" in Revelation, and it falls well before the events of Revelation 16, the only "great city" left is that of Jerusalem from 11:8. Meaning, 16:19 is pointing to the only remaining great city we have seen and the only one we have read about prior to this moment without explicitly naming this "great city" in 16:19 as Jerusalem.
Again, this is very distinct from the earthquake and judgment from the 6th seal. In the 6th seal, the mountains are moved, but not utterly removed. And if the mountains are removed in the 6th seal, how do the kings hide in the rocks? It seems simple; the 6th seal and this plague are not linked. The intensity of judgment grows from the 6th seal to now at the vials.
Linear Scene 1.5a: Only the Father is in the temple now. These vial or bowl plagues occur after the tribulation's pre-vial reaping and before the resurrection of those who died in the tribulation, which will happen in 20:4.