Turkish Frat Nehri Arabic Al-Furt River, Middle East. The largest river in Southwest Asia, it rises in Turkey and flows southeast across Syria and through Iraq. Formed by the confluence of the Kara and the Murat in the high Armenian plateau, the Euphrates descends between major ranges of the Taurus Mountains and drops nearly 1,000 ft (300 m) to the Syrian plateau. It then flows through western and central Iraq to unite with the Tigris and continues, as Shatt al-Arab, to the Persian Gulf. In all, it is 2,235 mi (3,596 km) long. Its valley was heavily irrigated in ancient times, and many great cities, some of whose ruins remain, lined its banks. With the Tigris, it defines an area known historically as Mesopotamia