This year has been particularly deadly, despite attempts by the government of Saudi Arabia to make the pilgrimage safer for the more than 3 million people who make the journey each year
A stampede at one of the last rituals of the season -- known as the "stoning of Jamarat," which symbolizes "stoning the devil," -- killed more than 700 people and injured hundreds more Thursday
So why incidents like this keep happening at the Hajj?
Here are some things you need to know.
Performing the Hajj is one of the five pillars of Islam, and every Muslim who is physically and financially able is required to make the journey to the holy city of Mecca near Saudi Arabia's west coast at least once in their lives.
At 9 a.m today there was a "sudden surge in the crowd" heading toward the Jamarat, resulting in overcrowding, a spokesman for the Saudi civil defense agency said in a statement from the Saudi Press Agency.
"A large number fell," the statement said.
Journalist Khaled Al-Maeena told CNN over the phone from Jeddah, Saudi Arabia, that pilgrims rushing to finish could have been the main reason for the stampede: "People like to do the first stoning in the morning," he said.
He added: "People must have fainted because it was very hot and humid down there ... and also there have been many cases of dehydration since yesterday."
The BBC has described it as the riskiest ritual of the Hajj because of the way worshipers jostle, which can knock weaker pilgrims over. The deadliest Hajj stampede killed 1,426 people and the Saudis have spent $1.2 billion on a bridge for pilgrims Although Losing one's life during the Hajj season is considered by many devout Muslims as an entry to heaven.
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