'Stronghold' in the Bible

And he brought them before the king of Moab: and they dwelt with him all the while that David was in the stronghold.

And the prophet Gad said unto David, Abide not in the stronghold; depart, and get thee into the land of Judah. Then David departed, and came into the forest of Hereth.

And David sware unto Saul. And Saul went home; but David and his men gat them up unto the stronghold.