This year, the holy gathering began at sun set on Sunday, 19 August 2018. Almost 2 million muslims from 80 different countries, traveled to Mecca for the 5 day pilgrimage.
All of the travellers (pilgrims) follow a series of religious rituals. The series of rituals were established by the Prophet Muhammad on his "farewell pilgrimage" to Mecca.
There are several different ways of performing the Hajj. Here are some important rituals they perform.
The Hajis or pilgrims, wear simple white cloth to show that they are equal.
The first day, the pilgrims travel from Mecca to the town of Mina. There they spend the day and night in enormous tent cities, praying, reading the Quran, and resting for the next day.
On the second day, the pilgrims leave Mina just after dawn to travel to the hill of Arafat. They climb to the top of Mount Arafat in order to pray — it is believed that Prophet Muhammad once gave a big speech there.
After sunset, its time to move again, this time to Muzdalifah - a 9 km trip - where they spend the night under the stars. Many will also begin collecting pebbles here for tomorrow's rites, departing again just before sunrise.
On the third day, the pilgrims move back to Mina. Here they throw stone pebbles at three pillars. Millions of pilgrims converge at the Jamarat Bridge, which houses the three pillars representing the devil. This act represents rejecting temptation or "stoning the devil."
On the last three days of the hajj, the pilgrims — they sacrifice a goat and celebrate Eid al-Adha, or the Festival of Sacrifice.
Then they return to the Grand Mosque in Mecca, where they will walk in counterclockwise circles seven times around a giant cube (called the Kaaba) in the center of the Grand Mosque. This is called a "farewell" tawaf.
The Kaaba - a black silk-clad stone structure at the heart of the Grand Mosque in Mecca - was built by the Prophet Abraham in biblical times.