The strong hold of Zion; either,
1. A very strong fort which fitly had built upon Mount Zion; which being taken, the city quickly yielded. Or,
2. The city of Zion, which was very strongly fortified.
Related Commentaries of 2 Samuel 5:7
2 Samuel 5:7
7 Nevertheless David took the strong hold of Zion: the same is the city of David.