Mecca, Saudi Arabia - Thousands and thousands of Muslim pilgrims are descending on Mecca for the Haj, the world's largest annual gathering. The main events begin Wednesday and Thursday marks the most important day, when all pilgrims assemble in the Arafat plain outside Mecca.

The pilgrimage ends after Aidiladha, or the Feast of Sacrifice, which will be celebrated on Friday. The Haj is one of the five pillars of Islam that every capable Muslim must perform at least once in lifetime. The bulk of pilgrims are from Asia, mostly from Indonesia which has the highest Haj quota.