Baghdad, capital of modern Iraq, was founded in the 8th century AD by the Abbasid caliph al-Mansur. He commissioned what he saw as an ideal city, one that would replace earlier regional capitals at Babylon and Ctesiphon in the Abbasid vision. The original plan of Baghdad was a series of concentric circles composed of residential and commercial buildings 2 km in diameter, dotted with parks and gardens intended to evoke the Koranic paradise. The influential Barmakid family from Balkh in Central Asia were instrumental in the implementation of this vision. This was not novel, as several ancient cities in Turkey and Persia also followed a circular plan. In short order Baghdad became what was likely the world's largest city and a hub for trade and learning. Under the Abbasids it was home to the famed Baytul-Hikmah or 'House of Wisdom', which gathered and supported some of the greatest minds of the Islamic world throughout the medieval period. It was here that many works in Greek, Persian and Sanskrit were translated into Arabic, congregating and preserving the ideas of scholars from far beyond the empire's physical or temporal boundaries.