Answer: Damascus and Baghdad.
Explanation:
During the Middle Ages, they were the most essential two centers of the Arab world. According to many historians, between the seventh and the tenth centuries, they were the largest and most developed centers of the world. A high culture and civilization developed in these cities. The development of science and the arts that were among the major segments of the development of the Arab Empire was impressive. The Abbasids moved the 750th capital of the empire from Damascus to Baghdad, which thus became the center of Islamic culture and science.
Under the leadership of Abbasid, Islamic civilization inherited and assimilated the traditions and achievements of many cultures. An incredibly rich culture flourished in the cities, with Baghdad, Cordoba leading, and Cairo. The rise of Islamic civilization was attended by all the nations that are lived under the rule of Islam, including Jews and Christians. Later, the capital was moved to Baghdad and destroyed by the Mongols. Because these were the two largest cities, the most significant number of people lived in them.
