The Hajj is an Islamic pilgrimage to Mecca and the largest gathering of Muslim people in the world every year. It is one of the five pillars of Islam, and a religious duty which must be carried out by every able-bodied Muslim who can afford to do so at least once in his or her lifetime.
The Hajj is a demonstration of the solidarity of the Muslim people, and their submission to God. The Hajj is associated with the life of the Prophet Muhammad from the 7th century, but the ritual of pilgrimage to Mecca is considered by Muslims to stretch back thousands of years to the time of Prophet Abraham.
Pilgrims join processions of hundreds of thousands of people, who simultaneously converge on Mecca for the week of the Hajj, and perform a series of rituals: Each person walks counter-clockwise seven times around the Kabah, runs back and forth between the hills of Al-Safa and Al-Marwah, drinks from the Zamzam well, goes to the plains of Mount Arafat to stand in vigil, and throws stones in a ritual stoning of the Devil.