Ether 13

It is from the prophet Ether, that we learn more concerning two cities...a New Jerusalem and a renewing of the old Jerusalem.  We learn that the land of the Jaredites would be -

"...the place of the New Jerusalem, which should come down out of heaven, and the holy sanctuary of the Lord."  (Book of Mormon  Ether 13:3)

"Coming down out of heaven" in my mind would be a city established upon the doctrines and teachings of heaven for -

"...concerning the house of Israel, and the Jerusalem from whence Lehi should come—after it should be destroyed it should be built up again, a holy city unto the Lord; wherefore, it could not be a new Jerusalem for it had been in a time of old; but it should be built up again, and become a holy city of the Lord; and it should be built unto the house of Israel.
6 And that a New Jerusalem should be built up upon this land, unto the remnant of the seed of Joseph, for which things there has been a type."  (Book of Mormon  Ether 13:5 - 6)

What is this type?

"For as Joseph brought his father down into the land of Egypt, even so he died there; wherefore, the Lord brought a remnant of the seed of Joseph out of the land of Jerusalem, that he might be merciful unto the seed of Joseph that they should perish not, even as he was merciful unto the father of Joseph that he should perish not.
8 Wherefore, the remnant of the house of Joseph shall be built upon this land; and it shall be a land of their inheritance; and they shall build up a holy city unto the Lord, like unto the Jerusalem of old; and they shall no more be confounded, until the end come when the earth shall pass away."  (Book of Mormon  Ether 13:7 - 8)

And who shall live in this "New Jerusalem"?

"...then cometh the New Jerusalem; and blessed are they who dwell therein, for it is they whose garments are white through the blood of the Lamb; and they are they who are numbered among the remnant of the seed of Joseph, who were of the house of Israel."  (Book of Mormon  Ether 13:10)

In my mind, this is not just the descendants of Nephi, but those who are declared descendants of Joseph.

I personally don't necessarily think this city is restricted to a distinct location as in cities of our day for Isaiah

"Enlarge the place of thy tent, and let them stretch forth the curtains of thine habitations: spare not, lengthen thy cords, and strengthen thy stakes;"  (Old Testament  Isaiah 54:2)

And -

"Look upon Zion, the city of our solemnities: thine eyes shall see Jerusalem a quiet habitation, a tabernacle that shall not be taken down; not one of the stakes thereof shall ever be removed, neither shall any of the cords thereof be broken."  (Old Testament  Isaiah 33:20)

Theses stakes which are part of Zion and the New Jerusalem will  ever be removed.  Therefore, I picture the New Jerusalem as massive tent that stretches to all habitations of stakes.