More than two million Muslims have gathered in Saudi Arabia's Mina Valley on the outskirts of the holy city of Mecca for the annual pilgrimage, or hajj. The white robed pilgrims -- from around the world -- head to Mount Arafat Monday for prayers. On Tuesday, the pilgrims take part in the symbolic stoning of the devil, throwing pebbles at three pillars. The ritual has been marred by deadly stampedes in the past, including the deaths of more than 240 pilgrims two years ago. Saudi officials reorganized access to the area this year in hope of avoiding another tragedy. On Thursday, a hostel for pilgrims in Mecca collapsed, killing 76 people. The hajj is a requirement of all able-bodied Muslims at least once in a lifetime.