Adullam - (Easton's Bible Dictionary)
One of the royal cities of the Canaanites, now Aid-el-ma (Josh. 12:15; 15:35). It stood on the old Roman road in the valley of Elah (q.v.), which was the scene of David's memorable victory over Goliath (1 Sam. 17:2), and not far from Gath. It was one of the towns which Rehoboam fortified against Egypt (2 Chr. 11:7). It was called "the glory of Israel" (Micah 1:15).
The Cave of Adullam has been discovered about 2 miles south of the scene of David's triumph, and about 13 miles west from Bethlehem. At this place is a hill some 500 feet high pierced with numerous caverns, in one of which David gathered together "every one that was in distress, and every one that was in debt, and every one that was discontented" (1 Sam. 22:2). Some of these caverns are large enough to hold 200 or 300 men. According to tradition this cave was at Wady Khureitun, between Bethlehem and the Dead Sea, but this view cannot be well maintained.