 The Western Desert, is about wide, from Mersa Matruh in Egypt to Gazala on the Libyan coast, along the "Via Balbia", the only paved road.The Great Sand Sea inland marks the southern limit of the desert at its widest points at Jaghbub (Giarabub) and Siwa Oasis; in British parlance, Western Desert came to include eastern Cyrenaica in Libya.From the coast, extending inland, there is a flat plain of stony desert, about above sea level, until it meets the Sand Sea.