'Fortress' in the Bible

in those days, when the king Ahasuerus sat on the throne of his kingdom, which was in Shushan the fortress,

And when these days were expired, the king made a feast to all the people that were present in Shushan the fortress, both to great and small, seven days, in the court of the garden of the king's palace.

and let the king appoint officers in all the provinces of his kingdom, that they may gather together all the young virgins of beautiful countenance to Shushan the fortress, to the house of the women, unto the custody of Hegai the king's chamberlain, keeper of the women; and let their things for purification be given.

There was in Shushan the fortress a certain Jew, whose name was Mordecai, the son of Jair, the son of Shimei, the son of Kish, a Benjaminite,

And it came to pass when the king's commandment and his decree was heard, and when many maidens were gathered together unto Shushan the fortress, unto the custody of Hegai, that Esther also was brought into the king's house, unto the custody of Hegai, keeper of the women.

The couriers went out, being hastened by the king's commandment, and the decree was given in Shushan the fortress. And the king and Haman sat down to drink; but the city of Shushan was in consternation.

The couriers mounted on coursers and horses of blood went out, being hastened and pressed on by the king's commandment. And the decree was given at Shushan the fortress.

And in Shushan the fortress the Jews slew and destroyed five hundred men.

On that day the number of those that were slain in Shushan the fortress was brought before the king.

And the king said to Esther the queen, The Jews have slain and destroyed five hundred men in Shushan the fortress, and the ten sons of Haman; what have they done in the rest of the king's provinces? And what is thy petition? and it shall be granted thee; and what is thy request further? and it shall be done.