In 2013, approximately 80 million people made the pilgrimage to Allahabad, India, arriving at a riverside metropolis that didn't exist a year prior -- and wouldn't exist two months later.

The pilgrims who make the trek to this spot are Hindus from all walks of life -- rich and poor, seekers and devotees. They cross the sacred Ganges River to a temporary city, built for their faith's most important event: the Kumbh Mela.

The Kumbh Mela is a sacred festival in which Hindus cleanse their sins by bathing in the water of the Ganges, a river believed to be a living goddess. This event is considered the biggest religious event on Earth as well as the largest gathering of human beings in the world.

To prepare for a record number of visitors, the Indian government had to build a city from the ground up, on land that is normally barren. It was no small feat. Here are some of the items they brought in:

• 35,000 toilets
• 22,000 street lights
• 38 hospitals
• 30 police stations
• 30 fire stations
• 18 pontoon bridges

Though the area of the Kumbh Mela is roughly half the size of Manhattan, it harbors nearly 30 times the population. These pilgrims travel from far and wide to bathe in the river -- Reshma, for example, is a 30-year-old career-oriented woman from Chicago who quit her job to make the long journey in search of a true connection to her faith. (Her story is detailed in the first episode of the seven-part documentary "Belief," premiering Oct. 18.)

After nearly two months, Reshma and the rest of the pilgrims returned to their homes. The temporary city returned to its former state. It will lie dormant until the next holy date, in 2019.

Explore more stories of diverse faiths in "Belief," airing every night from Oct. 18 to Oct. 24 at 8 p.m. ET on OWN.

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