The problem about the Elah Valley fortress Yosef Garfinkel has excavated at Khirbet Qeiyafa is that the people of Israel and Judah were still very close to their hill country village phase. Thus it is unexpected that they would build big administrative centers and public buildings around 1,000 BCE.
Saul seems to have done without big buildings. He typically made his headquarters under a tree (1 Samuel 14:2 and 22:6). It probably was no accident that they buried him under a tree (1 Samuel 31:13). It was where he was comfortable.
When David wanted a big building he imported skilled builders from Phoenicia.
As I thought about this yesterday, I saw something I had not considered or seen anybody else consider. Perhaps the outpost at Khirbet Qeiyafa was built by somebody else and captured by either Saul or David.
Navdad Na’aman thinks the site was Canaanite. He has some decent arguments. The structure is similar to some Canaanite sites. Canaanites seem to have not eaten pigs as much as you would think. So the lack of pig bones at the site does not tell against this theory.
Yosef Garfinkel has proposed that it was an administrative headquarters for David like the ones at Hebron and Jerusalem.
But Jerusalem was not built by the Judeans. David captured it and used it as his own fort, adding some buildings and the tent shrine.
Maybe something similar happened at Qeiyafa. Maybe some Canaanites city-state had built an outpost there to curb the Philistines. If Saul took it, it could have been his base in the Elah Valley as 1 Samuel 17 implies.
But if David took it later, it would solve the problem of why David had a fortress over against his ally, Gath. He didn’t build it. It served David more as an administrative center than as a bulwark.
One of the features of Qeiyafa is that there are what seem like little sanctuaries next to each gate. The sanctuaries have uncarved standing stones in them. Perhaps the Israelites replaced Baal idols with these to comply with the taboo against graven images.
One of the problems is that ancient texts do not give us the name of a well known city or encampment at this location. Garfinkel has discovered two gates so he says the place is Shaaraim mentioned in 1 Samuel 17:52. Shaaraim means two gates. However, many have trouble with this partly because they consider the battle in 1 Samuel 17 unhistorical.
The most popular other suggestion is that the place is Gob (2 Samuel 21:18-19), a place from which David’s mighty men operated.
These place names did not mean anything to later generations. 1 Chronicles 20:4 associates these battles with Gezer, presumably because it was a known place.