The Hajj is one of the pillars of Islam, which every adult Muslim must undertake at least once in their life if they can afford it and are physically able.
Every year about two million Muslims converge on Mecca - the holiest place in Islam - to take part in an event which combines piety and passion.
Many Muslims save for years in order to perform the pilgrimage. They often have to travel thousands of miles.
Then, once they arrive, they must brave vast crowds and the fierce heat of the desert as they perform the Hajj rituals.
In 2007, Hajj took place from December 17 to December 21.
