The 700-900m high region in the middle of the desert is the Hamad Plateau, a rather flat, stony semi-desert consisting of limestone bedrock covered with chert gravel. What little rain arrives on the plateau flows into local salt flats. The highest peaks of the Plateau are those of the 1000m+ Khawr um Wual in Saudi Arabia, and the 960m high Jebel Aneiza, at the border tripoint between Jordan, Iraq and Saudi Arabia.