18:21 Then a mighty angel picked up a boulder the size of a large millstone and threw it into the sea, and said:
“With such violence
the great city of Babylon will be thrown down,
never to be found again.
Then a MIGHTY ANGEL picked up a BOULDER the size of a large millstone and threw it into the SEA, and said:
When we compare these verses with Jeremiah 51:59-64, it appears that Jeremiah's prophesy is fulfilled here in the last days. In Jeremiah, the BOULDER is tied to the scroll containing the prophesy against Babylon. Then, interestingly, both the BOULDER and scroll are thrown into the Euphrates River which contained the 4 evil angels (Revelation 9:14). However, the Euphrates River has been dried up during the sixth bowl judgment (Revelation 16:12), so here the BOULDER is thrown into the SEA.
The BOULDER which looks like a millstone to John, requires a STRONG ANGEL to lift it. This can be interpreted as the event is bigger that any single human being could devise, or as the event is a crushing event much as the millstone grinds the grain, or, symbolically, as a judgment against anyone who cause a 'little one' to lose faith (Mark 9:38-42-50).
STONE/BOULDERS(S) in scripture are associated with life and the principles of life (Exodus 34:1-9, Luke 19:29-40, and 1 Corinthians 3:10-12-15). They represent our moral character and are tested by fire. If you are an unbeliever, you will give an accounting for your morals and deeds before the GREAT WHITE THRONE (Revelation 20:11-14).
“With such violenceThis is the VIOLENT END of Babylon (the global economy). The people inhabiting Babylon were so involved in materialism that they ignored God's laws (Exodus 34:1-9). As ruthless and violent that the Babylonian inhabitants were toward God's people, prophets, saints, and martyrs (verse 24), they will experience a similar VIOLENT END. Not only are the individuals terminated but the whole system (CITY) is terminated in a crushing blow.
In a broader symbolic sense, just as evil acts in Noah's day met their end in the great FLOOD (SEA) (Genesis 6:9-13-22), the evils of the end time materialistic world meet their end in the SEA. As discussed earlier, it is water/SEA that holds spirits, both good and evil. Thus it is fitting that this GREAT CITY/EVIL ends up in the SEA. Ultimately, the SEA, too, is completely destroyed (Revelation 21:1). The new heaven and new earth will NOT have any place to harbor EVIL. Praise the Lord!