The hajj, the annual Muslim pilgrimage to the Saudi Arabian city of Mecca, began Saturday. It changes every year depending on the location of the moon, but always happens during the eighth and the 12th of the month of Dhul Hijjah, the last month of the Islamic calendar. To find out more information about the hajj, continue reading below for some fast facts:

1. Muslims are required to make the journey at least once in their lifetime since the hajj is one of the five pillars of Islam. The only people who are exempt from the travel are those who cannot physical endure it or financially afford it.

2. Part of the hajj is being seen as equal in the eyes of God. That’s why men wear two pieces of white sheet—everyone’s wealth and social status are the same. Women’s clothing is less restrictive, but they must wear white and they can only show their hands and feet.

3. Unlike other Muslim rites, there isn’t any gender segregation at Hajj. Men and women are permitted to stand side by side.

4. The hajj takes place for five to six days, but the height of the festival occurs during Eid al-Adha, which is when Muslims commemorate the Prophet Abraham’s readiness to martyr his son.

5. Saudi Arabia has turned the hajj into a moneymaker. In the U.S., travel packages can cost up to $5,000.

6. The commercialization has led to people in the Muslim world criticizing the Saudi government.

7. Millions of people travel to the hajj, which has forced officials to limit the amount of people who participate in the pilgrimage.

8. A median of 9 percent of Muslims throughout the world said they participated in the pilgrimage to Mecca, according to a Pew poll.

9. To accommodate the millions who make the travel, Saudi Arabia has begun to expand the Grand Mosque in Mecca. In 2015, the crane fell over and tragically killed over 100 people days before the 2015 hajj was slated to start.

Hajj Millions of Muslims are preparing for the annual pilgrimage to Mecca, Saudi Arabia. Above, pilgrims pray inside the Grand Mosque as thousands circle the Kaaba in Mecca, Dec. 19, 2007. Photo: Reuters/Ali Jarekji

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