Khan Academy: Hajj: Islamic Middle East

One of the five pillars of Islam central to Muslim belief, Hajj is the pilgrimage to Mecca that every Muslim must make at least once in their lifetime if they are able; it is the most spiritual event that a Muslim experiences, observing rituals in the most sacred places in the Islamic world. Mecca is the birthplace of the Prophet Muhammad. The sanctuary there with the Ka'ba is the holiest site in Islam. As such, it is a deeply spiritual destination for Muslims all over the world; it is the heart of Islam.