Umar was the second muslim Caliph and reigned during 634 to 644 CE. This article details the reforms of Umar's era. Umar undertook many administrative reforms and closely oversaw public policy, establishing an advanced administration for newly conquered lands, including several new ministries and bureaucracies, as well as ordering a census of all the Muslim territories. During his reign, the garrison cities of Basrah and al-Kūfah were founded or expanded. In 638, he extended and renovated the Grand Mosque in Mecca and the Mosque of the Prophet in Medina. He also began the process of codifying Islamic law.