'Citadel' in the Bible

But Pekah the son of Remaliah, his officer, conspired against Pekahiah and struck him in Samaria, in the citadel of the king’s house, with Argob and Arieh; and with Pekah were fifty Gileadites. So he killed Pekahiah and became king in his place.

You saw that the breachesIn the wall of the City of David [the citadel of Zion] were many;You collected [within the city’s walls] the waters of the Lower Pool (Siloam).