When reading the Bible, the word Zion appears many different times and can be refer to multiple locations, according to the context.
Mount Zion
The most common location of Zion is Mount Zion, the easternmost hill in ancient Jerusalem.
According to the Bible, there was also a fortification on Mount Zion that King David captured through one of his campaigns, "David nevertheless captured the fortress of Zion" (2 Samuel 5:7).
City of David
With this in mind, King David proceeded to call Mount Zion the "City of David."
Dwelling of God
The Temple also became associated with Mount Zion, which n the Bible was referred to as God's dwelling place.
Heavenly Jerusalem
Combining all of these connections, Christians began to associate Zion with the "Heavenly Jerusalem," as the "Lamb of God" is seen on Mount Zion in the book of Revelation.
Zion is a powerfully evocative word in the Bible. It helps us look backward as well as forward, to when we will all dwell on "Mount Zion" with the Lamb of God.