An annual ritual, performed uninterrupted for centuries, has begun in Islam's most holy city.
Every year, during the new moon of the Islamic lunar month of Dhul-Hijjah, millions of Muslims from all over the world descend upon Mecca.
The pilgrimage, known as hajj, is one of the five pillars of the Islamic faith. Up to 2 million people from some 100 nations are participating in this year's hajj.
Mecca is the birthplace of the Prophet Mohammad, founder of the Islamic faith. Every Muslim who can afford to make the hajj is obliged to do so at least once during his or her lifetime.
One of the first rituals of the hajj was performed, as more than a million people stood shoulder-to-shoulder and prayed while circling the Kaaba -- a stone building believed to be t he world's first sanctuary dedicated to the worship of one God. A symbol of unity, the Kaaba is a cornerstone of the Islamic faith. All over the world, Muslims orient themselves in the direction of the Kaaba every time they bow to pray.
Hajj activities, some of which are mandatory, climax on the ninth day of Dhul-Hijjah. On that day, the pilgrims travel to the site of Mount Arafat, where Mohammad preached his last sermon 14 centuries ago.
A day later, on the high holiday known as Eid al-Adha, Muslims worldwide gather for communal prayers, and begin their sacred feast.
Animals are sacrificed to commemorate God's test of Abraham, who was to sacrifice his son Isaac, or Ishmael in Islam, but was permitted to kill a ram instead.
Saudi officials estimate some 700,000 sheep and more than 20,000 cattle and camels will be sacrificed by the pilgrims this year.