Two million people travel to the holy cities in Saudi Arabia each year to participate in the hajj pilgrimage, which Muslims believe cleanses the soul and wipes away sins. Over 50,000 security forces have been deployed in response to terrorism fears and to prevent stampeding and other problems that have plagued the annual hajj in recent years.
"I feel so enlightened and so much closer to Allah that I can barely wait to stand on the mountain of mercy," said Afzal Sikandar Khan, 45, a pilgrim from India, referring to Mount Arafat, recognized as the place where the Prophet Muhammad delivered his last sermon.
Many pilgrims remain concerned about numerous hazards such as stampedes and fires that have killed hundreds of pilgrims in recent years.
"I will pray for the tsunami victims, but my immediate concern is that Allah enables us to complete our pilgrimage safe and sound," said Nigerian doctor Mokhtar Ahmed, 30.
In addition to the burdens of hosting 2 million visitors, Saudi authorities have expressed concerns about terrorism and the spread of diseases. The kingdom has mobilized counter-terror squads and set up medical centers to treat sick pilgrims.
The site of the stoning ritual where pilgrims have been stampeded has been developed to smooth the flow of pilgrims. A stampede last year left 244 pilgrims dead and another in 1990 killed 1,426 people.
The pilgrims begin the rituals by first circling the Kaaba, a large stone structure that Muslims face during their five daily prayers. They then continue to spend a night in the tent city of Mina, and head the next day to pray at Mount Arafat, the central rite of the pilgrimage.
The pilgrims later head to Muzdalifah, where they collect pebbles overnight, and throw pebbles the next day at three pillars symbolizing the devil. Many pilgrims then shave or trim their hair as a symbol of rebirth.
A camel, sheep or cow is slaughtered the day after the hajj to mark the beginning of Eid al-Adha, or the Feast of the Sacrifice. More than a million sheep have been imported for slaughter.
Saudi Arabia set up the tent city in Mina with more than 40,000 white, fireproof tents to house the pilgrims. Dozens of trucks will roam the streets, offering food and drink.
Dozens of fire engines will be on standby in the city surrounded by colossal mountains. High winds in 1997 swept fire through a sprawling tent city for pilgrims, killing more than 340 and injuring 1,500.
The pilgrimage is required of able-bodied Muslims at least once in a lifetime, if they can afford it. Pilgrims travel to the cities of Mecca, Mina, Arafat and Muzdalifa.