Adullam was a town in the low hills of western Judah, about nineteen kilometres east of Gath1 and twenty-four kilometres due west of Bethlehem.2 It is listed as a city of Judah in Joshua 15:35, and the cave where David stayed was likely nearby/in the vicinity. The town itself was a fortress city (Joshua 15:33–35; 2 Chronicles 11:7).3
1 David departed from there and escaped to the cave of Adullam. And when his brothers and all his father’s house heard it, they went down there to him.