Yemen is located in Southwest Asia, at the southern tip of the Arabian Peninsula, between Oman and Saudi Arabia. It is situated at the entrance to the Bab-el-Mandeb Strait, which links the Red Sea to the Indian Ocean (via the Gulf of Aden) and is one of the most active and strategic shipping lanes in the world. Yemen has an area of , including the islands of Perim at the southern end of the Red Sea and Socotra at the entrance to the Gulf of Aden. Yemen's land boundaries total . Yemen borders Saudi Arabia to the north () and Oman to the northeast (). Through the Socotra island, Yemen also shares borders with the Guardafui Channel and the Somali Sea. Topography Yemen occupies the southern end of the Arabian Plate. The country's mountainous interior is surrounded by narrow coastal plains to the west, south, and east and by upland desert to the north along the border with Saudi Arabia. The Tihamah is a nearly long, semidesert coastal plain that runs along the Red Sea and is part of the Arabian Peninsula coastal fog desert ecoregion. The highland regions are interspersed with wadis, or river valleys, that are dry in the winter months (Yemen has no permanent rivers.) Most notable is the Wadi Hadhramaut in eastern Yemen, the upper portions of which contain alluvial soil and floodwaters and the lower portion of which is barren and largely uninhabited. Both the eastern plateau region and the desert in the north are hot and dry with little vegetation. In the northeastern Empty Quarter, sands highlight the region, being the largest expanse of sand in the world. It receives little to no rain for extensive periods of time. Little vegetation grows here either. The central highlands are drier than the western highlands because of rain-shadow influences, but still receives sufficient rain in wet years for extensive cropping. Its diurnal temperature variations are among the highest in the world: ranges from in the day to at night are normal. Water storage allows for irrigation and the growing of wheat and barley while the western highlands are famous for sorghum, coffee, and some tropical fruits like bananas and mangos. Elevation Yemen is a continuously elevated country, with only the coastal plains being the lowest-lying areas. Jagged peaks and plateaus cover most of Yemen, and the average elevation in the country is about . The interior