Bible Verses About Walls: Were probably often strengthened with plates of iron or brass

I will make you to this people a fortified bronze wall; and they shall fight against you, but they shall not prevail against you; for I am with you to save you and to deliver you, says the LORD.

Take for yourself an iron pan, and set it for a wall of iron between you and the city: and set your face toward it, and it shall be besieged, and you shall lay siege against it. This shall be a sign to the house of Israel.