Explanation:

The Tigris is the eastern of the two great rivers that define Mesopotamia, the other being the Euphrates. The river flows south from the mountains of southeastern Turkey through Iraq and empties into the Persian Gulf. Baghdad is the capital of Iraq and the second-largest city in the Arab world after Cairo. Located along the Tigris River, the city was founded in the 8th century and became the capital of the Abbasid Caliphate.