'Fortified Cities' in the Bible

Declare ye in Judah, and publish in Jerusalem; and say, Blow ye the trumpet in the land: cry aloud and say, Assemble yourselves, and let us go into the fortified cities.

And they shall eat up thy harvest, and thy bread, which thy sons and thy daughters should eat; they shall eat up thy flocks and thy herds; they shall eat up thy vines and thy fig-trees; they shall beat down thy fortified cities, wherein thou trustest, with the sword.

Why do we sit still? assemble yourselves, and let us enter into the fortified cities, and let us be silent there; for Jehovah our God hath put us to silence, and given us water of gall to drink, because we have sinned against Jehovah.

when the king of Babylon's army was fighting against Jerusalem, and against all the cities of Judah that were left, against Lachish and against Azekah; for these alone remained of the cities of Judah as fortified cities.