More than two million Muslims from around the globe on Sunday started the hajj pilgrimage at Islam's holiest sites in Saudi Arabia, one of the world's largest annual gatherings.
The ultra-conservative kingdom, which is undergoing dramatic social and economic reforms, has mobilised vast resources for the six-day journey, one of the five pillars of Islam.
"It's the dream of every Muslim to come here to Mecca," Frenchman Soliman Ben Mohri said.
"It's the ultimate journey. What worries me is the return to my normal life. For the moment, I am in a dream," the 53-year old told AFP.
Every Muslim is required to complete the hajj at least once in their lifetime if they have the means to do so.
Tens of thousands of security personnel have been deployed for the pilgrimage, which was struck by its worst ever disaster three years ago when around 2,300 worshippers were crushed to death in a stampede.
This year, the Saudis have launched a "smart hajj" initiative, with apps to help pilgrims with everything from travel plans to medical care.
The interior ministry said on Saturday that the number of pilgrims arriving in Mecca had already surpassed the two million mark, mostly from abroad including large contingents from Egypt, India, Pakistan and Bangladesh.
Most of the pilgrims began moving on Sunday from Mecca to the nearby Mina valley where they will spend the night in fire-resistant tents.
Thousands of buses and vehicles carrying the pilgrims lined the eight kilometre (five-mile) road from Mecca to Mina. Many pilgrims made the journey walking under the scorching heat of the sun.
On Monday, pilgrims will climb nearby Mount Arafat for the climax of the hajj, praying and reading the Koran.
The prophet Mohammed delivered his final sermon from Mount Arafat to Muslims who had accompanied him on his final hajj, according to Islam.
After sunset, pilgrims head to Muzdalifah, half-way between Arafat and Mina, where they stay at least until midnight.
They gather pebbles to perform the symbolic stoning of the devil on the eve of the Eid al-Adha feast, which marks the end of hajj.
This year's pilgrimage comes with the oil-flush kingdom witnessing unprecedented change, including an end to a ban on women driving.
While rights campaigners have welcomed the reforms, they have also expressed alarm about a crackdown on dissent.
Although the kingdom's young de facto leader, Crown Prince Mohammed bin Salman, has spearheaded the changes, religion remains a key force in Saudi Arabia.