Baghdad is the capital of Iraq, as well as the coterminous Baghdad Governorate. 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.