The word(s) "fortress" appears 4 time(s) in 4 verse(s) in Quran in Saheeh International translation.

(1) And take for yourselves palaces and fortresses that you might abide eternally?

(2) And He brought down those who supported them among the People of the Scripture from their fortresses and cast terror into their hearts [so that] a party you killed, and you took captive a party.

(3) It is He who expelled the ones who disbelieved among the People of the Scripture from their homes at the first gathering. You did not think they would leave, and they thought that their fortresses would protect them from Allah; but [the decree of] Allah came upon them from where they had not expected, and He cast terror into their hearts [so] they destroyed their houses by their [own] hands and the hands of the believers. So take warning, O people of vision.

(4) Indeed, it throws sparks [as huge] as a fortress,