The region extends south from the mountains of Anatolia, east from the hills on the left bank of the Euphrates river, west from the mountains on the right bank of the Tigris river and includes the Sinjar plain. It extends down the Tigris to Samarra and down the Euphrates to Hit. The Khabur River runs for over 400 km (250 mi) across the plain, from Turkey in the north, feeding into the Euphrates.
The major settlements are Mosul, Deir ez-Zor, Raqqa, Al Hasakah, Diyarbakır and Qamishli. The western, Syrian part, is essentially contiguous with the Syrian Al-Hasakah Governorate and is described as "Syria's breadbasket". The eastern, Iraqi part, includes and extends slightly beyond the Iraqi Ninewa Governorate. In the north it includes the Turkish provinces of Şanlıurfa, Mardin, and parts of Diyarbakır Province.
The name al-Jazira has been used since the 7th century AD by Islamic sources to refer to the northern section of Mesopotamia, which together with the Sawād, made up al-‘arāq (Iraq). The name means "island", and at one time referred to the land between the two rivers, which in Aramaic is Bit Nahren. Historically, the name could be restricted to the Sinjar plain coming down from the Sinjar Mountains, or expanded to embrace the entire plateau east of the coastal ranges. In pre-Abbasid times the western and eastern boundaries seem to have fluctuated, sometimes including what is now northern Syria to the west and Adiabene in the east.
Al-Jazira is characterised as an outwash or alluvial plain, quite distinct from the Syrian Desert and lower-lying central Mesopotamia; however the area includes eroded hills and incised streams. The region has several parts to it. In the northwest is one of the largest salt flats in the world, Sabkhat al-Jabbul. Further south, extending from Mosul to near Basra is a sandy desert not unlike the Empty Quarter. In the late 20th and early 21st centuries the region has been plagued by drought.
Al-Jazirah is extremely important archeologically. This is the area where the earliest signs of agriculture and domestication of animals have been found, and thus the starting point leading to civilization and the modern world. Al-Jazirah includes the mountain Karaca Dağ in southern Turkey, where the closest relative to modern wheat still grows wild. At several sites (e.g. Hallan Çemi, Abu Hureyra, Mureybet) we can see a continuous occupation from a hunter-gathering lifestyle (based on hunting, and gathering and grinding of wild grains) to an economy based mainly on growing (still wild varieties of) wheat, barley and legumes from around 9000 BC (see PPNA). Domestication of goats and sheep followed within a few generations, but didn't become widespread for more than a millennium (see PPNB). Weaving and pottery followed about two thousand years later.