The Western Desert of Egypt is an area of the Sahara which lies west of the river Nile, up to the Libyan border, and south from the Mediterranean sea to the border with Sudan. It is named in contrast to the Eastern Desert which extends east from the Nile to Red Sea. The Western Desert is mostly rocky desert, though an area of sandy desert, known as the Great Sand Sea, lies to the west against the Libyan border. The desert covers an area of 680,650 km2 which is two-thirds of the land area of the country.