'Fenced Cities' in the Bible

Now in the fourteenth year of king Hezekiah did Sennacherib king of Assyria come up against all the fenced cities of Judah, and took them.

Hast thou not heard long ago how I have done it, and of ancient times that I have formed it? now have I brought it to pass, that thou shouldest be to lay waste fenced cities into ruinous heaps.