The Hajj is one of the pillars of Islam, which every adult Muslim must undertake at least once in their life if they can afford it and are physically able.
Circling the Kaaba in the Great Mosque in Mecca is part of the ritual
Every year about two million Muslims converge on Mecca - the holiest place in Islam - to take part in an event which combines piety and passion.
Many Muslims save for years in order to perform the pilgrimage. They often have to travel thousands of miles.
Then, once they arrive, they must brave vast crowds and the fierce heat of the desert as they perform the Hajj rituals.
For the host country, Saudi Arabia, the event has a special importance. Saudi rulers are acutely conscious of their responsibility as custodians of the Muslim holy places.
2006: 345 die in a crush during a stone-throwing ritual
2004: 251 trampled to death in stampede
2003: 14 are crushed to death
2001: 35 die in stampede
1998: At least 118 trampled to death
1997: 343 pilgrims die and 1,500 injured in fire
1994: 270 killed in stampede
1990: 1,426 pilgrims killed in tunnel leading to holy sites
1987: 400 die as Saudi authorities confront pro-Iranian demonstration
The sheer number of pilgrims poses formidable problems. In recent years hundreds have died as a result of demonstrations, fires, stampedes - or just sunstroke and exhaustion.
The Saudi authorities have introduced a quota system to keep down the numbers of pilgrims. They have also tried, and failed, to keep politics out of the Hajj.
In 1987 hundreds of pilgrims were killed in clashes between the Saudi security forces and Iranian-led demonstrators.
The Hajj step by step:
To carry out the pilgrimage rituals a pilgrim needs to be in a state of Ihram - a special state of ritual purity.
A pilgrim does this by making a statement of intention to perform the Hajj, wearing special white clothes (which are also called Ihram), and obeying certain regulations.
During the Hajj, pilgrims are forbidden to:
- Engage in marital relations
- Shave or cut their nails
- Use cologne or scented oils
- Kill or hunt anything
- Fight or argue
- Women must not cover their faces, even if they would do so in their home country
- Men may not wear clothes with stitching.
Once in Mecca pilgrims enter the Great Mosque and walk seven times round the Kaaba (a cube-like building in the centre of the mosque) in an anti-clockwise direction. This is known as Tawaf. Pilgrims also run seven times along a passageway in the Great Mosque, commemorating a search for water by Hajar, wife of the Prophet Abraham.
DAY 1: FIRST STEP
Pilgrims travel to Mina on 8 Dhul Hijjah (a date in the Islamic calendar) and remain there until dawn the next morning.
DAY 2: STANDING AT ARAFAT
Pilgrims then travel to the valley of Arafat and stand in the open praising Allah and meditating.
At the end of the day, pilgrims travel to Muzdalifa where they spend the night. Pilgrims gather up stones to use the next day.
DAY 3: STONING THE DEVIL
In the morning, pilgrims return to Mina and throw seven stones at pillars called Jamaraat. These represent the devil. The pillars stand at three spots where Satan is believed to have tempted the Prophet Abraham.
Pilgrims sacrifice an animal (usually a sheep or goat). This commemorates the incident related in the Old Testament when the Prophet Abraham was about to sacrifice his son and God accepted a sheep instead. Nowadays many pilgrims pay someone to slaughter the animal on their behalf.
Pilgrims shave their heads or cut some hair from it and return to the Great Mosque at Mecca for a further Tawaf, walking around the Kaaba. They then return to Mina, where they spend the night.
DAYS 4 & 5
Pilgrims spend time in Mina, continuation of the ritual of stoning the pillars.
If a pilgrim has been unable to return to Mecca to walk around the Kaaba, he or she does so on the fourth or fifth day.
STAGES OF THE PILGRIMAGE BY DAY
The Hajj takes place over five days