Baghdad (Arabic: بغداد‎, Baġdād, IPA: [bæɣˈdæːd]) is the capital of Republic of Iraq, as well as the coterminous Baghdad Governorate. The population of Baghdad as of 2011 is approximately 7,216,040, making it the largest city in Iraq,[1][2] the second largest city in the Arab World (after Cairo, Egypt), and the second largest city in Western Asia (after Tehran, Iran).

Located along the Tigris River, the city was founded in the 8th century and became the capital of the Abbasid Caliphate. Within a short time of its inception, Baghdad evolved into a significant cultural, commercial, and intellectual center for the Islamic World. This in addition to housing several key academic institutions (e.g. House of Wisdom) garnered the city a worldwide reputation as the "Center of Learning". Throughout the High Middle Ages, Baghdad was considered to be the largest city in the world with an estimated population of 1,200,000 people.[3] The city was largely destroyed at the hands of the Mongol Empire in 1258, resulting in a decline that would linger through many centuries due to frequent plagues and multiple successive empires. With the recognition of Iraq as an independent state (formerly the British Mandate of Mesopotamia) in 1938, Baghdad gradually regained some of its former prominence as a significant center of Arabic culture.
Reference: http://en.wikipedia.org/wiki/Baghdad,_Iraq