Millions of people have come to Mecca for the Hajj pilgrimage, one of the world's largest annual gatherings. The pilgrimage is a central pillar of the Islamic faith, a spiritual journey meant to cleanse the faithful of sin and bring them closer to God. This year's Hajj pilgrimage takes place from 22 to 26 September. Recommended:Performing actions that equal to Hajj in rewardRecommended:Hajj manifestation of Muslim unity, Iran’s Leader says