The "city" is referring to the new Jerusalem, part of the new Heaven and new Earth.
Revelation 21:1-4
"Then I saw “a new heaven and a new earth,”[a] for the first heaven and the first earth had passed away, and there was no longer any sea. 2 I saw the Holy City, the new Jerusalem, coming down out of heaven from God, prepared as a bride beautifully dressed for her husband. 3 And I heard a loud voice from the throne saying, “Look! God’s dwelling place is now among the people, and he will dwell with them. They will be his people, and God himself will be with them and be their God. 4 ‘He will wipe every tear from their eyes. There will be no more death’[b] or mourning or crying or pain, for the old order of things has passed away.”"
What city is this ?
The "city" is referring to the new Jerusalem, part of the new Heaven and new Earth.
Revelation 21:1-4 "Then I saw “a new heaven and a new earth,”[a] for the first heaven and the first earth had passed away, and there was no longer any sea. 2 I saw the Holy City, the new Jerusalem, coming down out of heaven from God, prepared as a bride beautifully dressed for her husband. 3 And I heard a loud voice from the throne saying, “Look! God’s dwelling place is now among the people, and he will dwell with them. They will be his people, and God himself will be with them and be their God. 4 ‘He will wipe every tear from their eyes. There will be no more death’[b] or mourning or crying or pain, for the old order of things has passed away.”"
https://www.biblegateway.com/passage/?search=Revelation+21
oh, ok.