Islam, the Muslim religion, originated in the Arabian Peninsula around 622. Islam's prophet, Muhammad, lived in Mecca, a city in the western part of the peninsula. Here he developed the core doctrines of the religion.
Because of the central importance of Mecca in Islam, every able-bodied Muslim who has enough money must hake a pilgrimage to that city at least once in his lifetime. Islam also developed in Medina, a city around 270 miles from Mecca. Muhammad fled to this city for ten years after the elites of Mecca drove him out at the beginning of his ministry.
From these cities, Islam quickly spread across the Arabian Peninsula, the Middle East and North Africa. By the early years of the 8th century, rulers governing in the name of Islam governed territories spreading from modern-day India to modern-day Spain.