'Castle' in the Bible

The words of Nehemiah son of Hacaliah:Now it happened in the month of Chislev, in the twentieth year [of the Persian king], as I was in the capitol of Susa,

I put my brother Hanani, with Hananiah the commander of the fortress, in charge of Jerusalem, for Hananiah was a more faithful and God-fearing man than many [of the others].

in those days when King Ahasuerus sat on his royal throne which was at the citadel in Susa [the capital of the Persian Empire],

A brother offended is harder to win over than a fortified city,And contentions [separating families] are like the bars of a castle.