Hundreds of thousands of Muslim pilgrims flooded a valley near the Saudi holy city of Mina on Monday to stone pillars representing Satan

Hundreds of thousands of Muslim pilgrims flooded a valley near the Saudi holy city of Mina on Monday to stone pillars representing Satan, on the penultimate day of the annual hajj.

Pilgrims rushed to throw 21 stones on the three pillars that symbolize the devil, the last rite of the annual and compulsory pilgrimage to the Saudi city of Mecca, the birthplace of Islam and its holiest site.
  
To complete the ritual, pilgrims must throw seven pebbles at each of three 25-metre (82-foot) pillars on the first day of the three-day Eid al-Adha feast marking the end of the hajj, and another seven on each of the last two days.
  
Pilgrims then make their way to Mecca's Great Mosque for a "farewell visit" to the Kaaba, Islam's most sacred relic.
  
Tuesday is the third and final day of the stoning ritual and once complete, will mark the end of the hajj.

The hajj is one of the five pillars of Islam and must be performed at least once in a lifetime by all those who are able to make the journey.