SUNSET SUNDAY, OCTOBER 13: The world’s largest annual religious gathering commences in Mecca today, with more than 3 million Muslims having traveled by land, sea and air to perform one of the five Pillars of Islam: Hajj. (Note: The Hindu Kumbh Mela is a larger gathering, but it only occurs every three years.)

Calculating the Dates: Muslims follow a lunar calendar and religious observances are marked by moon sightings. Saudi astronomical experts have announced Oct. 14 as the official date that Hajj pilgrims will gather at Mount Arafat (thus meaning that Hajj begins at sunset on Oct. 13, and Eid Al-Adha will begin at sunset on Oct. 14—and the day of Oct. 15. Read more from Al Arabiya. An earlier story in Al Arabiya also includes a helpful info-graphic of the Ka’aba. (Note: English spellings of Arabic words vary widely across news sources and websites.)

Health, safety and the MERS Coronavirus: The Saudi Minister of Health recently announced the 2013 safety plan for this year’s Hajj pilgrims. Along with the increased number of healthcare workers at all facilities in Mecca, Medina and other holy sites, preparations have been made for the Middle East Respiratory Syndrome Coronavirus (MERS-CoV), which appeared in Saudi Arabia last year and has since been reported in several countries in Europe and Africa. While working in coordination with the World Health Organization and health organizations from each country that sends pilgrims, the Saudi government has asked that the elderly, children and the chronically ill avoid Hajj this year in light of the dangers of MERS-CoV.

Grand Mosque construction: With the number of Hajj pilgrims growing every year, expansion projects have been underway in the Grand Mosque—the holiest site in Islam and the home of the Ka’aba—for almost 90 years. Yet the current expansion project, worth $21.3 billion and dubbed the “project of the century, has been underway since 2011. The first portions of the project will be open to accommodate this year’s Hajj pilgrims. (Al Arabiya reported.) The temporary mataf bridge that was installed during Ramadan also will service crowds performing the tawaf (circumambulation of the Ka’aba) this Hajj. Along with better accommodations for handicapped pilgrims, two floors of the new annex will also accommodate this year’s pilgrims, reported the Saudi Gazette.

Did you know? The number of pilgrims attending Hajj has increased by 1 million during the past decade. In 2003, just over 2 million pilgrims performed Hajj; in 2013, more than 3 million are expected.

The entire Grand Mosque expansion project, which will take several years to complete, will expand the mosque in three main areas: the expansion of the Al-Haram, to accommodate 2 million worshipers; the development of exterior areas, such as rest rooms and tunnels; and a support services area, which will include a district cooling plant, electricity station and water stations. Once completed, the Grand Mosque’s capacity will almost double.

HAJJ: THE EXPERIENCE OF A LIFETIME

Each year for 14 centuries, Muslims have journeyed to Mecca for Hajj. Warring nations, drought and dangerous terrain have not stopped pilgrims from completing the final Pillar of Islam and following in the footsteps of the Prophet Muhammad. Though today’s pilgrims experience far fewer obstacles on the way to Hajj than their ancestors did—who, in years past, often took a year or more to travel to Mecca by foot and claimed countless casualties along the way—the holiness of the Hajj remains unchanged.

The massive crowds in recent years present new problems: catering to both the medical and basic needs of 3 million people has proven no easy feat. With such masses, cases of trampling, heat exhaustion and contagious viruses are not uncommon. Still, in a city designed to host the Hajj, surrounding infrastructure has been tailored specifically to this once-a-year event. “It is truly amazing,” commented Rajeeb Razul, a journalist from the Philippines. “To organize a gathering of humans this large, for housing them, for feeding them and for meeting their every need year after year must be a monumental task.”

As crowds of Muslims begin arriving in Mecca, most often by airplane but also by sea and foot, Hajj begins aboard one of 15,000 buses that delivers pilgrims to their destination. During the duration of Hajj, pilgrims will visit the Grand Mosque, the Plain of Arafat, the Valley of Mina and the stone pillars at Jamarat. (In 2004, the stone pillars were replaced by long walls with catch basins, to accommodate the growing number of Hajj participants.) From Mecca, this year’s crowd of 3 million will walk eight miles to the Plain of Arafat, which now houses a sea of misting sprinklers to cool the colossal crowd. Chilled water and food is available for pilgrims, who will spend the day at Arafat, performing set rituals and pleading for God’s forgiveness at the Mount of Mercy.

Most rituals of Hajj commemorate the life of Abraham, who is believed to have built the Ka’aba.

The joyful Eid Al-Adha will begin at sunset on Monday, October 14. (Due to differences in moon sightings, it is expected to occur in North America one day later, though the date varies worldwide by region.)

ENJOY A PERSONAL OVERVIEW OF THE HAJJ

Read The Spirit invited Imam Steve Elturk, a noted figure in interfaith circles, to write a detailed overview of this epic pilgrimage—so non-Muslims can get a sense of the personal story of a pilgrim moving through these sacred sites.