‘And I saw the holy city, new Jerusalem, coming down out of heaven from God, made ready as a bride adorned for her husband.'
See Revelation 21:9-10. This descent is on the new earth, the new creation. The creation of Genesis 1 is no more, except in the sense that it has been the prototype of the new creation. The idea is that just as God created the old world and then created man to people it, so now, having created the new unpopulated earth He sends down from Heaven the city of His people (compare Hebrews 12:22), to the prepared place (compare John 14:3). And the people descend together as a city (for they were previously in Heaven - Revelation 14:1-3) and are one together and form the bride. The holy city has put on her beautiful garments (Isaiah 52:1) and is as a bride adorned for her husband.
That Jerusalem is the bride parallels Revelation 19:7 and the wording is very similar, demonstrating that the new Jerusalem is to be seen as representing the people of God. The bride was a composite figure, for she consisted of the whole people of God, and the new Jerusalem is the same, for in the end a city is its people. Compare how in Matthew 8:34 ‘all the city came out to meet Jesus' (a city ‘coming out' is similar to a city ‘coming down'. See also Matthew 11:20; Matthew 12:25; Matthew 21:10; Mark 1:33; Mark 6:11; Luke 4:43; Acts 13:44; Acts 14:21; Acts 17:5; Acts 17:16). Thus it is now ‘the holy city'. Previously His people were the holy sanctuary (Revelation 11:1) in which God dwelt (1 Corinthians 3:16; 1 Corinthians 6:19), now they are seen as one with, and part of, the holy city wherein God will dwell (v. 3). Jerusalem is created a rejoicing and her people a joy (Isaiah 65:18). This is the work of the Amen (Isaiah 65:16), and the former troubles will be forgotten (v. 17).