'Stronghold' in the Bible

Nevertheless David took the stronghold of Zion; the same is the city of David.

David lived in the stronghold, and called it the city of David. David built around from Millo and inward.

When the Philistines heard that they had anointed David king over Israel, all the Philistines went up to seek David; and David heard of it, and went down to the stronghold.

David was then in the stronghold; and the garrison of the Philistines was then in Bethlehem.

and came to the stronghold of Tyre, and to all the cities of the Hivites, and of the Canaanites; and they went out to the south of Judah, at Beersheba.