Friday’s deadly crane collapse at Masjid al-Haram, the Grand Mosque of Mecca, has so far killed 107 people, and injured 238. Here’s more information about the largest and most sacred mosque in the world.

It’s the most sacred site in Islam

Photo by Thamer Al-Hassan on Flickr.

Originally built during the reign of Caliph Omar Ibn al-Khattab (634-644), the mosque has seen many renovations and expansions, especially in the 8th and 14th centuries. The current mosque mainly dates to 1571.

The mosque itself was built around the Kaaba, also known as the House of Allah. It’s a structure that Muslims believe predates Islam and was first built by the prophet Ibrahim and his son Ismail as a place of worship. During the time of the Prophet Muhammed (570-632) the Black Stone, which is in the Ka’ba became a holy Muslim relic, according to historvius.com

View images of the Grand Mosque of Mecca over time

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It’s the major site to serve religious duty in Islam

With a total area of 356,000 square meters (3,831,952 square feet) the mosque can accommodate up to 770,000 worshippers. One of the five pillars of Islam states that every Muslim is obligated to perform haj once in their lifetime if they have the financial means.

During the week of the haj, an annual pilgrimage of Muslims around the world to Mecca, Muslims converge on the city to perform a series of rituals, including the circling of the cube-shaped Kaaba, praying and holding vigil at Mount Arafat, and performing the symbolic stoning of the devil by throwing pebbles at the three pillars in Mina.

Prayers on and around the mount are a climactic emotional and spiritual moment in the haj. The faithful believe that on that day the gates of heaven are open, prayers are answered and past sins are forgiven.

Photo by 3omar Faruq on Flickr.

All male pilgrims, regardless of wealth or status, wear seamless terry white cloths to symbolize equality before God during the haj. Women cover their hair and wear long loose clothing, forgoing makeup and other adornments to help them detach from worldly pleasures and outward appearances.

It was on Mount Arafat, marked by a white pillar, where Islam’s Prophet Muhammad is believed to have delivered his last sermon to tens of thousands of followers some 1,400 years ago, calling on Muslims to unite.

While following a route that the prophet once walked, the rites are believed to ultimately trace the footsteps of the prophets Ibrahim and Ismail, or Abraham and Ishmael as they are named in the Bible.

It’s been the site of several tragic events

The millions of pilgrims who visit the country’s holy sites each year pose a considerable security and logistical challenge for the Saudi government, and large-scale deadly accidents have occurred on a number of occasions in years past.

Smoke rising from the Grand Mosque during the assault on the Marwa-Safa gallery in 1979.

On occasion, the haj and events surrounding it have been marred by accidents and tragedies, such as Friday’s crane collapse on the Grand Mosque in Mecca that left at least 107 dead. In the heavy traffic, crushes and pileups have killed hundreds in the past. Here’s a look at some deadly haj-related incidents:

More info: Crane collapses at Mecca mosque in Saudi Arabia, 107 killed

2015: At least 107 people are killed and scores wounded when a crane collapses in bad weather, crashing onto the Grand Mosque in Mecca, Islam’s holiest site.

2006: More than 360 pilgrims are killed in a stampede at the desert plain of Mina, near Mecca, where pilgrims carry out a symbolic stoning of the devil by throwing pebbles against three stone walls. The day before the haj began, an eight-story building being used as a hostel near the Grand Mosque in Mecca collapsed, killing at least 73 people.

2004: A crush of pilgrims at Mina kills 244 pilgrims and injures hundreds on the final day of the haj ceremonies.

2001: A stampede at Mina during the final day of the pilgrimage ceremonies kills 35 haj pilgrims.

1998: About 180 pilgrims are trampled to death in panic after several of them fell off an overpass during the final stoning ritual at Mina.

1997: At least 340 pilgrims are killed in a fire at the tent city of Mina as the blaze was aided by high winds. More than 1,500 were injured.

1994: Some 270 pilgrims are killed in a stampede during the stoning ritual at Mina.

1990: The worst haj-related tragedy claims the lives of 1,426 pilgrims in a stampede in an overcrowded pedestrian tunnel leading to holy sites in Mecca.

1979: The mosque was at the centre of a rebellion against the Saudi royal family when it was seized by a group of several hundred Islamic militants led by Juhaymān al-ʿUtaybī and Muḥammad bin ʿAbd Allāh al-Qaḥṭānī, After obtaining a religious ruling sanctioning the use of force within the Great Mosque, where violence is forbidden, government troops retook the mosque in a bloody battle.

Story compiled with information from the Associated Press.