And I saw a new heaven and a new earth: for the first heaven and the first earth were passed away; and there was no more sea. And I John saw the holy city, new Jerusalem, coming down from God out of heaven, prepared as a bride adorned for her husband.
(Rev 21:1-2)

And there came unto me one of the seven angels which had the seven vials full of the seven last plagues, and talked with me, saying, Come hither, I will show thee the bride, the Lamb's wife. And he carried me away in the spirit to a great and high mountain, and showed me that great city, the holy Jerusalem, descending out of heaven from God,
(Rev. 21:9-10)

The angel said, "Hey John, come here. I'm gonna show you the bride of Christ!"

What did he show him?

Abraham looked for a city which hath foundations, whose builder and maker is God. (Hebrews 11:10)

Except the Lord build the house, they labour in vain that build it. (Psalm 127:1)

Upon this rock I will build my church (Matt 16:18)

Abraham was looking for the Church!

New Jerusalem is not complete yet! It is still being built by God. We are right now setting in heavenly places. We have already come to the New Jeurusalem, though.

But ye are come unto mount Zion, and unto the city of the living God, the heavenly Jerusalem, and to an innumerable company of angels, To the general assembly and church of the firstborn, which are written in heaven, and to God the Judge of all, and to the spirits of just men made perfect,
(Heb 12:22-23)

And Hebrews' context above was speaking of the New Covenant as opposed to the Old Covenant.  If we are in the New City, and it's supposed to be understood as being a physical city, then where is it?  I see no actual jasper walls anywhere around me.