The Great Sand Sea is a roughly lung-shaped area of sandy desert lying astride the border with Libya, 200 miles inland from the Mediterranean. The sea is divided by a long peninsula of rocky desert along the border, leaving the eastern lobe in Egypt and the western in Libya, where it is called the Calanshio desert. On the Egyptian side it extends from a point south of Siwa for 400 miles into the interior, to a point north of the Jebel Uweinat.[3][4][5]