The Islamic caliphate originally overseen by Muhammad and his successors would eventually fragment. One of the most dominant successor states was the Abbasid Caliphate.Seen here at its largest extent (around 850 CE), the Abbasids would control vast amounts of land between 750 and 1258 CE.

Abbasids850 by Gabagool (Own work) [CC-BY-3.0 (http://creativecommons.org/licenses/by/3.0)], via Wikimedia Commons
A Description of Baghdad
The work of Ibn Sina, an Arab Physician