After this I looked, and behold, a door standing open in heaven! And the first voice, which I had heard speaking to me like a trumpet, said, “Come up here, and I will show you what must take place after this.” 2 At once I was in the Spirit, and behold, a throne stood in heaven, with one seated on the throne. 3 And he who sat there had the appearance of jasper and carnelian, and around the throne was a rainbow that had the appearance of an emerald. 4 Around the throne were twenty-four thrones, and seated on the thrones were twenty-four elders, clothed in white garments, with golden crowns on their heads. 5 From the throne came flashes of lightning, and rumblings and peals of thunder, and before the throne were burning seven torches of fire, which are the seven spirits of God, 6 and before the throne there was as it were a sea of glass, like crystal.
And around the throne, on each side of the throne, are four living creatures, full of eyes in front and behind: 7 the first living creature like a lion, the second living creature like an ox, the third living creature with the face of a man, and the fourth living creature like an eagle in flight. 8 And the four living creatures, each of them with six wings, are full of eyes all around and within, and day and night they never cease to say,
“Holy, holy, holy, is the Lord God Almighty,
who was and is and is to come!”
9 And whenever the living creatures give glory and honor and thanks to him who is seated on the throne, who lives forever and ever, 10 the twenty-four elders fall down before him who is seated on the throne and worship him who lives forever and ever. They cast their crowns before the throne, saying,
11 “Worthy are you, our Lord and God,
to receive glory and honor and power,
for you created all things,
and by your will they existed and were created.” Revelation 4
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Let's look at some history of the time this letter was written.

There were twenty-four recognized religions in Rome and each religion had a priest that surrounded Cesar. Christianity and Judaism was not part of these religions. Like the pharisees of Judaism, these pagan priest were very public and attended governmental meetings, olympic games and parties, and other government events. History tells us these priests were always wearing white robes and golden crowns, with golden sashes around their waists.

Before you get concerned on what you're reading, remember that John is using what the people knew to describe what he was seeing. This does not mean that John was saying these pagan priest were around the throne room.

It's debated but I believe that Revelation was written near the end of the reign of Emperor Domitian. Emperor Domitian lead one of the most brutal persecutions in church history and that's why I believe it was during this period that the letter was penned. During this time, Ephesus had the largest colosseum in the world and Sardis had the second largest, which was being built at this time.
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On the outside of the Sardis colosseum is a gate that had ox heads and wreaths. Each emperor had a different animal that represented them and we see this depiction on the belt of the statue of Emperor Domitian outside this colosseum.
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There is record of the rise of Domitian and his choosing Ephesus as his capital city. He planned his arrival to the city to coincide with the grand opening of the colosseum. One can only imagine the speculative arrival of Domitian, when seeing movies depicting the arrival of an emperor into a city. With his arrival, the twenty four priest would assemble around him as well.

Around the throne is rumbling, peals of thunder, and lightning and this is a reference back to Mount Sinai. When people look back to this reference of Sinai and the mightiness of the display of God they see this same picture in the throne room.

“Holy, holy, holy is the Lord Almighty;
the whole earth is full of his glory.” Isaiah 6:3

We see this reference to the beautiful song in Isaiah about the worthiness of God and his Glory. I can picture the song resonating in their mind, like an ear-worm, like the modern version may be resonating in yours now. And if so, you're getting a picture of what it was like to be the first century Asia Minor church reading this letter of hope from John.