It is a rite that all followers of Islam are supposed to perform at least once in a lifetime, yet for the rest of the globe the hajj is veiled in mystery.
Now the British Museum in London has opened the first ever major exhibition on the pilgrimage, to give non-Muslims a glimpse of the heart of this world religion.
"This exhibition is for everybody, Muslims and non-Muslims, everyone who wants to know more about this extraordinary phenomenon, which is one of the great religious manifestations of the world," said Neil MacGregor, the director of the museum.
"Hajj is the only part of the practice of Islam that non-Muslims can’t see.
"It seems very important to try to explore that experience and to understand what it means to Muslims now, what it has meant through the centuries and to understand how that habit of pilgrimage has changed the world."
It has taken three years and deals with museums around the world to bring together the exhibition.
The show uses priceless artifacts, video footage, personal audio recordings and photographs to explore the history, journeys and experiences of millions of pilgrims who travel from around the world to reach the holy city of Mecca every year.
The hajj is one of the five pillars of Islam and must be performed at least once in a lifetime by all those who are able to. It takes place during the last month of the Islamic year known as Dhu’l Hijja.
For centuries the hajj was an epic undertaking involving weeks of travel on foot or on the back of a camel, in convoys across mountains and deserts; or months at sea across the Indian Ocean at risk from shipwreck or pirates.
Among the artifacts on display is a "Mahmal," one of the ceremonial curtained transports in which the Sultans were carried from Cairo to Mecca in what is now Saudi Arabia, and a Quran from the eighth century.
Also on show is "Milestone," one of the stone slabs once used by pilgrims in Iraq to mark their route to Mecca, so they could find their way home.
In a modern touch, "Magnetism," a minimalist piece of art by Saudi artist Ahmed Mater, uses iron filings to depict pilgrims circling around the Kaaba, the sacred cube-shaped building in Mecca.
Muslims believe the Kaaba was built by Ibrahim and his son Ismail.
The show also features the experiences of several western travelers who succeeded in entering Mecca, whether in disguise like British explorer Richard Burton in 1853, who wrote a book about his experiences, or legitimately like Scottish noblewoman Evelyn Cobbold, who adopted Islam, and visited in 1933.
The Hajj exhibition is the third by the British Museum in a series of sacred spiritual journeys that included "Treasures of Heaven" and "Book of the Dead," and is intended to improve understanding of the pilgrimage and Islam itself.
"We had to contact museums from all over the world to request if we could borrow some of their artifacts, and if there were items that related to the routes of Hajj," said curator Venetia Porter.
Many of the artifacts were donated by Nasser Khalili, one of the biggest collectors of Islamic art in the world.
"This exhibition is a journey that sends out a religious, spiritual, ritual and cultural message that proves how harmonious Islam is," Khalili told AFP.
However the exhibition, organized in partnership with the King Abdulaziz Public Library in Riyadh, skirts over some of the modern problems the hajj faces.
With huge numbers of pilgrims attending — around three million last year —there have been stampedes in the past, with 364 people dying in 2006, 251 in 2004 and 1,426 in 1990.
"Hajj: Journey to the Heart of Islam" opened at the British Museum on Jan. 26, and runs until April 15.