'Walled' in the Bible

And David said to Abishai, Sheba, the son of Bichri, will do us more damage than Absalom did; so take some of your lord's servants and go after him, before he makes himself safe in the walled towns, and gets away before our eyes.

And he said, The Lord is my Rock, my walled town, and my saviour, even mine;

And to the walled town of Tyre, and to all the towns of the Hivites and the Canaanites: and they went out to the South of Judah at Beer-sheba.