Blessed are they that do his commandments, that they may have right to the tree of life, and may enter in through the gates into the city.
Are you thinking that is talking about heaven???
That is the new Jerusalem. We inhabit it in heaven for the first 1000 years. Then Christ brings it to earth for the rest of eternity.
THE BIBLICAL TRUTH ABOUT THE MILLENNIUM
http://www.aloha.net/~mikesch/millen.htm
You've got it backwards! That city is on earth during the 1000 years of Christ's reign with a rod of iron. Why would He need a rod of iron and why would "the nations" need healing if we/they are all in heaven??? Do you read the book of Revelation? It is the millennial reign of Christ ON earth and when that is over, He creates a new heaven and new earth wherein dwells righteousness. And I heard a loud voice from the throne saying: “Behold, the dwelling place of God is with man, and He will dwell with them. They will be His people, and God Himself will be with them as their God. ‘ He will wipe away every tear from their eyes,’ and there will be no more death or mourning or crying or pain, for the former things have passed away.” And the One seated on the throne said, “Behold, I make all things new.” (Rev. 21:3-5)