What does it mean to have a strong city according to the Bible?

The concept of a 'strong city' in biblical literature, particularly as mentioned in Isaiah 26, symbolizes the ultimate security and refuge that God provides for His people. This city is not merely a physical location but a representation of a spiritual reality where God's promises are fulfilled. It serves as an assurance to believers that they are protected by the walls of His salvation and righteousness. This strong city is established by God's eternal counsel, underlining that their safety lies in His immutable character and covenants. Believers are then invited to find solace in this strong city, anchored in the assurance of God's grace and the completed work of Christ.