'Fortress' in the Bible

I looked in the vision and it seemed that I was at the citadel of Susa, [the capital of Persia], which is in the province of Elam; and I looked in the vision and I saw myself by the Ulai Canal.

But out of a branch of her [familial] roots will one (her brother, Ptolemy III Euergetes I) arise in his place, and he will come against the [Syrian] army and enter the fortress of the king of the North, and he will deal with them and will prevail.

“His sons will prepare for battle and assemble a multitude of great forces; which will keep on coming and overflow [the land], and pass through, so that they may again wage war as far as his fortress.