Muslim pilgrims cast stones at pillars symbolising Satan in Mena November 18, 2010. Millions flock to Mecca in Saudi Arabia for the annual haj pilgrimage, a duty for every able-bodied Muslim who can afford it. Muslims around the world celebrate Eid al-Adha to mark the end of the haj by slaughtering sheep, goats, cows and camels to commemorate Prophet Abraham's willingness to sacrifice his son Ismail on God's command. REUTERS/Mohammed Salem (SAUDI ARABIA - Tags: RELIGION SOCIETY IMAGES OF THE DAY)