'Strongholds' in the Bible

David stayed in the wilderness in the strongholds, and remained in the hill country in the wilderness of Ziph. Saul sought him every day, but God didn't deliver him into his hand.

Then the Ziphites came up to Saul to Gibeah, saying, "Doesn't David hide himself with us in the strongholds in the wood, in the hill of Hachilah, which is on the south of the desert?

David went up from there, and lived in the strongholds of En Gedi.