'Citadel' in the Bible

Then David the king said to all the assembly, "God has chosen Solomon my son alone, a young man and inexperienced, and the work [is] great, for the citadel [is] not for humankind, but for Yahweh God.

Grant to Solomon my son a heart of peace to keep your commands, your statutes, and your regulations to do everything, and to build the citadel for which I have provided."