'Stronghold' in the Bible

Even so, David captured the stronghold of Zion, which is now known as the City of David.

When the Philistines eventually learned that Israel had anointed David to be king over Israel, they marched out in search of him. But David heard about it and retreated to his stronghold.

Meanwhile, Joab attacked the Ammonite city of Rabbah and captured its stronghold.

This is what he said: LORD, you are my stone stronghold and my fortified place; you are continuously delivering me.

David was living in that stronghold at the time, while a Philistine garrison was then at Bethlehem.