The second vision John wrote about occurred in heaven. The vision was of an area in heaven where God’s throne is. Everything that John recorded until Revelation chapter 17 happened in this vision.
What John saw first was like what other prophets had seen in visions of God’s throne. Those visions are recorded in 1 Kings 22:19, Isaiah chapter 6, Ezekiel 1:26–28 and Daniel 7:9–10. The things John saw were signs of God’s complete power and glory.
The rainbow showed God’s splendour and glory. In the Bible the rainbow is a sign of God’s mercy.
John heard and saw the 24 elders and the four living creatures worshipping God. Together they are a picture of God being praised for ever by all of creation.