Al-Ahsa rewards those who come prepared for a desert oasis that is also one of humanity's oldest continuously inhabited places. The UNESCO World Heritage site encompasses not just palm groves but a layered landscape of Ottoman forts, ancient mosques, geological formations, and natural springs. Start in Hofuf — the historic market and Ibrahim Palace can fill a morning — then head northeast to the Jabal Qarah caves in the afternoon, when the desert light softens and the cave temperatures feel most welcome against the heat outside.