Many references are made in the book of Revelation to the book of Daniel. We are told the book of Daniel is sealed until the end times. So also would the book of Revelation be sealed.
The book described in Revelation 5:1 is sealed with seven seals. The whole chapter is devoted to the question, who is worthy to open the seals?
For many, the person who unseals the book of Revelation is John N. Darby. Or one of his followers. Others suppose rationalist German critics unravelled its mysteries. Or, insert your favourite commentator. But in Revelation 5:12, Jesus Christ is the only one found worthy, in heaven and earth, to open the seals of the book. As I understand this, it teaches that to understand the book of Revelation, our minds need to be enlightened by Christ. He unlocks and unseals the book to us, not Mr. Darby, or any other person; only Jesus can open our minds to its meaning.
On the question about whether Babylon in chapters 17 and 18 is a literal city, Daniel's prophecies illuminate the significance of Babylon in Revelation. Daniel acknowledged that God is the one who reveals secrets.
Daniel answered in the presence of the king, and said, The secret which the king hath demanded cannot the wise men, the astrologers, the magicians, the soothsayers, shew unto the king;
But there is a God in heaven that revealeth secrets, and maketh known to the king Nebuchadnezzar what shall be in the latter days. Thy dream, and the visions of thy head upon thy bed, are these;
As for thee, O king, thy thoughts came into thy mind upon thy bed, what should come to pass hereafter: and he that revealeth secrets maketh known to thee what shall come to pass.
But as for me, this secret is not revealed to me for any wisdom that I have more than any living, but for their sakes that shall make known the interpretation to the king, and that thou mightest know the thoughts of thy heart.
Daniel was given the true interpretation of the king's dream. It reveals the meaning of Babylon in prophecy.
Thou, O king, sawest, and behold a great image. This great image, whose brightness was excellent, stood before thee; and the form thereof was terrible.
This image's head was of fine gold, his breast and his arms of silver, his belly and his thighs of brass,
His legs of iron, his feet part of iron and part of clay.
Thou sawest till that a stone was cut out without hands, which smote the image upon his feet that were of iron and clay, and brake them to pieces.
Then was the iron, the clay, the brass, the silver, and the gold, broken to pieces together, and became like the chaff of the summer threshingfloors; and the wind carried them away, that no place was found for them: and the stone that smote the image became a great mountain, and filled the whole earth.
Here is a great image, and as Daniel explains the vision, the image represents all the great human kingdoms, that are eventually broken, and reduced to chaff, and the kingdom of God takes their place.
This is the dream; and we will tell the interpretation thereof before the king.
Thou, O king, art a king of kings: for the God of heaven hath given thee a kingdom, power, and strength, and glory.
And wheresoever the children of men dwell, the beasts of the field and the fowls of the heaven hath he given into thine hand, and hath made thee ruler over them all. Thou art this head of gold.
And after thee shall arise another kingdom inferior to thee, and another third kingdom of brass, which shall bear rule over all the earth.
And the fourth kingdom shall be strong as iron: forasmuch as iron breaketh in pieces and subdueth all things: and as iron that breaketh all these, shall it break in pieces and bruise.
And whereas thou sawest the feet and toes, part of potters' clay, and part of iron, the kingdom shall be divided; but there shall be in it of the strength of the iron, forasmuch as thou sawest the iron mixed with miry clay.
And as the toes of the feet were part of iron, and part of clay, so the kingdom shall be partly strong, and partly broken.
And whereas thou sawest iron mixed with miry clay, they shall mingle themselves with the seed of men: but they shall not cleave one to another, even as iron is not mixed with clay.
And in the days of these kings shall the God of heaven set up a kingdom, which shall never be destroyed: and the kingdom shall not be left to other people, but it shall break in pieces and consume all these kingdoms, and it shall stand for ever.
Forasmuch as thou sawest that the stone was cut out of the mountain without hands, and that it brake in pieces the iron, the brass, the clay, the silver, and the gold; the great God hath made known to the king what shall come to pass hereafter: and the dream is certain, and the interpretation thereof sure.
The image's head represented Nebuchadnezzar's kingdom, called Babylon, implying that the whole image can be called "Babylon." This underlies John's use of the term Babylon in Revelation, IMO. It represents the world, human civilization. The image described in Daniel 2 includes all human governments and society.
In Revelation 11:8, John alludes to this "great city," as symbolic of the whole world, outside Jerusalem. Jesus was crucified outside Jerusalem; he "suffered without the gate." [Heb. 13:12]
Jerusalem itself is the holy city of the saints, the "camp of the saints" and the "beloved city," which represents the church, the heavenly Jerusalem.
This also leads to the proper interpretation of the wilderness, in Rev. 12:6, 14, and Rev. 17:3.
Those who have "escaped the corruption that is in the world," [2 Pet. 1:4] come out of Babylon, and go to a spiritual "wilderness."
The sojourn of the Israelites in the wilderness before they came to the promised land is a metaphor and a figure of the church's present state. [1 Cor. 10:1-11; 2 Pet. 2:1]
Egypt and Sodom were places from which God's people escaped. They represent the bondage of sin, and the world. The world's social systems, governments, philosophies, and religions are represented by the great city Babylon, in Revelation 18:1-4. Verse 4 says, "And I heard another voice from heaven, saying, Come out of her, my people, that ye be not partakers of her sins, and that ye receive not of her plagues."
In Rev. 12:6 and 14 the woman flees to the wilderness, and has a place prepared by God, and is nourished there. Jesus said to his disciples, "In my Father's house are many mansions: if it were not so, I would have told you. I go to prepare a place for you. And if I go and prepare a place for you, I will come again, and receive you unto myself; that where I am, there ye may be also." [John 14:2-3] The place prepared for her by God represents the spiritual environment in which Christians dwell in all ages of the church. Like the Israelites who camped in many different places in the wilderness, the church has persevered through various spiritual and cultural environments, over the centuries, and today exists in all nations.
The "place" prepared for the woman in Rev. 12:6 and Rev. 12:14 is no doubt the same as the "place" Jesus prepares for the saints in John 14, which is called a wilderness, as it is separate and distinct from the world.
And in Rev. 17:3, John said he was taken to the wilderness, from where he saw the woman who sat on the beast. He said, "And upon her forehead was a name written, Mystery, Babylon The Great, The Mother Of Harlots And Abominations Of The Earth." [Rev. 17:5]
From the wilderness, a place outside of, and separate from the world-system, John described the woman riding the beast. That is how we need to understand it too. The "fornication" of the woman refers to her involvement with the world, and its politics, governments, nations, and society.
James wrote: "Ye adulterers and adulteresses, know ye not that the friendship of the world is enmity with God? whosoever therefore will be a friend of the world is the enemy of God." [James 4:4]