D&C 45

 As the Lord reveals doctrine concerning a New Jerusalem, he explains - 

"...it shall be called the New Jerusalem, a land of peace, a city of refuge, a place of safety for the saints of the Most High God;

67 And the glory of the Lord shall be there, and the terror of the Lord also shall be there, insomuch that the wicked will not come unto it, and it shall be called Zion.

68 And it shall come to pass among the wicked, that every man that will not take his sword against his neighbor must needs flee unto Zion for safety."  (Doctrine and Covenants 45:66–68)

It becomes apparent to me that "Zion" is not limited to a single city for we later learn - 

"Arise and shine forth, that thy light may be a standard for the nations;

6 And that the gathering together upon the land of Zion, and upon her stakes, may be for a defense, and for a refuge from the storm, and from wrath when it shall be poured out without mixture upon the whole earth."  (Doctrine and Covenants 115:5–6)