The English Standard Version (ESV) titles Psalm 48: Zion, the City of Our God. You can read in 2 Samuel 5 the account of David’s conquest of Zion and the establishment of his kingdom in Jerusalem. During David’s reign, Zion came to mean the city of God.

In David’s day, worship of God centered in a physical city on a geographical mountain. Psalm 48 begins by extolling God and crafting a language landscape evoking majestic mountains and strong towers:

Great is the Lord and greatly to be praised
    in the city of our God!
His holy mountain, beautiful in elevation,
    is the joy of all the earth,
Mount Zion, in the far north,
    the city of the great King.
Within her citadels God
    has made himself known as a fortress (Psalm 48:1-3, ESV).

The glimpse of God’s kingdom inspires believers to praise their great God, but those who gather together to attack the Lord see it and tremble.

For behold, the kings assembled;
    they came on together.
As soon as they saw it, they were astounded;
    they were in panic; they took to flight.
Trembling took hold of them there,
    anguish as of a woman in labor.
By the east wind you shattered
    the ships of Tarshish.
As we have heard, so have we seen
    in the city of the Lord of hosts,
in the city of our God,
    which God will establish forever. Selah (Psalm 48:4-8, ESV).

God’s enemies will be utterly confounded. They will panic and flee. God will shatter their ships. But his city stands firm forever. Pause to consider that (Selah).

As God’s people think on these things, they rejoice  (Psalm 48:9-11, ESV).

We have thought on your steadfast love, O God,
    in the midst of your temple.
As your name, O God,
    so your praise reaches to the ends of the earth.
Your right hand is filled with righteousness.
    Let Mount Zion be glad!
Let the daughters of Judah rejoice
    because of your judgments! 

Believers focus on God’s love as they worship him. God’s name is revered throughout the earth, and his praise reverberates around the world. God’s judgment against his enemies as well as his love toward his children display his righteousness. Let Christ’s church be glad! Let all God’s children rejoice!

Israelite believers could walk around the actual walls of Jerusalem, but modern Christians walk in the Lord.

Walk about Zion, go around her,
    number her towers,
consider well her ramparts,
    go through her citadels,
that you may tell the next generation
    that this is God,
our God forever and ever.
    He will guide us forever (Psalm 48:12-14, ESV).

God is our fortress. Christ’s kingdom fills the earth. God never fails and he will guide us forever. Think about it. Believe it. Tell your children that this is our God.