How is God's holiness revealed in the City of God?

The holiness of God is a central theme in the understanding of the City of God. Within its walls, God's character is made known, and the holiness of Christ is exalted. Psalm 48 portrays the city as beautiful for its elevation, indicating that it stands apart from worldly cities. The inhabitants of this city recognize their own unworthiness contrasted with God's holiness. It is only through union with Christ that they can attain holiness, as He alone is the standard by which they are judged. This emphasizes the need for a blood sacrifice to approach God, echoing the Old Testament's sacrificial system, fulfilled in Christ's atoning work.