Rev 21:2 And I John saw..... The Holy City, New Jerusalem, coming down from God out of heaven, prepared as a bride adorned for her husband.
Galatians 4:25-26 ...
Hebrews 12:22 one is earthy and the home of the believers during the Millennial period.
The other is heavenly as the New Jerusalem or Celestial City hover over the earth during the thousand year millennial reign of Christ and then becomes situated eternally upon earth at the end of the thousand year period.
Revelation 21:1-8 actually follows 21:9 -22:15. This is one time the chronological outline of the book of Revelation is different.
God Bless
Love123