What do we know about walls? They’re great for hanging pictures on. They’re great for having a place to put the roof of a house. How are they for security?
Well, the most famous wall in the world is the Great Wall of China, built over a period of 600 years beginning in the 7th century and reaching its greatest fortifications during the Ming Dynasty of the 14th century. It never actually stopped raids across it, and was completely breached in 1644.
Then there is the “Western Wall,” the last surviving wall of the Temple in Jerusalem.