The annual Islamic pilgrimage draws millions of visitors each year, making it the largest yearly gathering of people in the world.
More than 2 million Muslims began the annual hajj pilgrimage on Sunday in Saudi Arabia, circling the cube-shaped Kaaba from first light in Mecca that Islam's faithful face five times each day during their prayers.
The five-day hajj pilgrimage represents one of the world's biggest gathering every year, a trip required of all able-bodied and financially-able Muslims once in their life.
"We are very blessed by Allah to be in this place, and we pray to Allah to make the Islamic nations from the West to the East in a better situation," said Essam-Eddin Afifi, a pilgrim from Egypt.
The Kaaba represents the metaphorical house of God and the oneness of God.
Muslims circle the Kaaba counter-clockwise seven times while reciting supplications to God, then walk between the two hills traveled by Hagar. Mecca's Grand Mosque, the world's largest, encompasses the Kaaba and the two hills.
Before heading to Mecca, many pilgrims visit the city of Medina, where the Prophet Muhammad is buried and where he built his first mosque.
Muslims believe the hajj retraces the footsteps of the Prophet Muhammad, as well as those of the prophets Ibrahim and Ismail — Abraham and Ishmael in the Bible.
After prayers in Mecca, pilgrims will head to an area called Mount Arafat on Monday, where the Prophet Muhammad delivered his final sermon. From there, pilgrims will head to an area called Muzdalifa, picking up pebbles along the way for a symbolic stoning of the devil and a casting away of sins that takes place in the Mina valley for three days.
At the hajj's end, male pilgrims will shave or cut their hair and women will cut a lock of hair in a sign of renewal for completing the pilgrimage. Around the world, Muslims will mark the end of hajj with a celebration called Eid al Adha. The holiday, remembering Ibrahim's willingness to sacrifice his son, sees Muslims slaughter sheep and cattle, distributing the meat to the poor.
Maj. Gen. Mansour al Turki, the spokesman of the Saudi Interior Ministry, told journalists on Saturday that over 2 million Muslims from abroad and inside the kingdom would be taking part in this year's hajj.
For Saudi Arabia, the hajj is the biggest logistical challenge the kingdom faces. Its ruling Al Saud family stakes its legitimacy in part on its management of the holiest sites in Islam. King Salman's official title is the "Custodian of the Two Holy Mosques," at Mecca and Medina. Other Saudi kings, and the Ottoman rulers of the Hijaz region before them, all have adopted the honorary title.
The kingdom has spent billions of dollars of its vast oil revenues on security and safety measures, particularly in Mina, where some of the hajj's deadliest incidents have occurred.
The worst in recorded history took place only three years ago. On September 24, 2015, a stampede and crush of pilgrims in Mina killed at least 2,426 people, according to an Associated Press count.