'Strongholds' in the Bible

And they put him in a cage with nose-rings, and brought him to the king of Babylon; they brought him into strongholds, that his voice should no more be heard upon the mountains of Israel.

Say thou thus unto them, Thus saith the Lord Jehovah: As I live, verily they that are in the waste places shall fall by the sword, and him that is in the open field will I give to the beasts to be devoured, and they that are in the strongholds and in the caves shall die of the pestilence.