Baghdad

Founded in 762 AD by al-Mansur on a site with settlement dating back to at least the Neo-Babylonian period, Baghdad became the capital of the Abbasid Caliphate and its most notable development project. The city evolved into an intellectual and cultural center. This, in addition to housing several key academic institutions, including the House of Wisdom, as well as a multi-ethnic and multi-religious environment, garnered it a worldwide reputation as the "Center of Learning". For much of the Abbasid era, during the Islamic Golden Age, Baghdad was one of the largest cities in the world and rivaled Chang'an, as the population peaked at more than one million. It was largely destroyed at the hands of the Mongol Empire in 1258, resulting in a decline that would linger for many centuries due to frequent plagues and shifts in power between multiple successive empires. Later, Baghdad served as the administrative center of Ottoman Iraq, exercising authority over the provinces of Basra, Mosul, and Shahrizor.