The Umayyad Dynasty began in 661 when Muawiya, an Umayyad leader, took control of the Islamic Empire that had been growing since the time of Mohammad. The Umayyad Dynasty lasted until 750 when the Abbasids overthrew the Umayyads. During this time, the capital of the Islamic Empire was moved to Damascus. The Empire expanded across North Africa and then across the Strait of Gibraltar and into the Iberian Peninsula. They also expanded the empire east into central Asia. The Umayyads are known for establishing Arabic as the official language of the empire. They also established a common coinage. These coins were engraved with Arabic quotations from the Koran. The Umayyad Mosque in Damascus and the Dome of the Rock in Jerusalem are two of the most important architectural achievements of the Umayyads. These two great structures are some of the most revered places next to mosques in Medina and Mecca. Most of the greatest Islamic achievements in bookmaking, literature, mathematics, astronomy and medicine took place after the overthrow of the Umayyads by the Abbasids. One of the Umayyads, Abd al Rahman escaped to the Iberian Peninsula after the overthrow of the Umayyads. There, in 756, he established a new Umayyad Dynasty. During the Umayyad Dynasty in Spain, Cordoba became its leading city. Cordoba, under the Umayyad became a center of learning, containing 70 libraries, the largest with over 500,000 volumes. Thousands attended the university and law school there. The Great Mosque in Cordoba is another of the Umayyad achievements. The Muslim Empire in Spain lasted until 1492 when Isabella and Ferdinand drove the last Muslims out of Spain.