In the early eighth century, the Visigothic Kingdom was invaded by the Umayyad Caliphate, ushering in over 700 years of Muslim rule in Southern Iberia. During this period, Al-Andalus became a major economic and intellectual center, with the city of Córdoba being among the largest and richest in Europe. Several Christian kingdoms emerged in the northern periphery of Iberia, chief among them León, Castile, Aragón, Portugal, and Navarre. Over the next seven centuries, an intermittent southward expansion of these kingdoms—metahistorically framed as a reconquest, or —culminated with the Christian seizure of the last Muslim polity, the Nasrid Kingdom of Granada, and the control of all Iberia by the Christian kingdoms in 1492. That same year, Christopher Columbus arrived in the New World on behalf of the Catholic Monarchs, whose dynastic union of the Crown of Castile and the Crown of Aragon is usually considered the emergent Spain as a unified country. During the centuries after the Reconquista, the Christian kings of Spain persecuted and expelled ethnic and religious minorities such as Jews and Muslims through the Spanish Inquisition.