Adullam is an ancient ruin once numbered among the thirty-six cities of Canaan whose kings "Joshua and the children of Israel smote". After that, it fell as an inheritance to the tribe of Judah and was included in the northern division of the Shephelah "lowland" cities of the land of Judah.
The connection between Judah and Adullam and its surroundings was actually already established in the patriarchal period, when Judah "went down from his brothers and turned aside to a certain Adullamite, whose name was Hirah". At the beginning of the royal period, in the days of King Saul, the area was close to the land of the Philistines, and thus David, fleeing from Saul, sought refuge in the cave of Adullam and made it a place of reconnoitering and organization, both, for him and his men.
Wikipedia https://en.wikipedia.org/wiki/Adullam
Address Israel
Coordinates 31°39'2.244" N 35°0'7.32" E