San Francisco Frontiers - India's Hindu pilgrims: a sea of humanity at Kumbh Mela

The millennia-old Kumbh Mela, a show of religious piety and ritual bathing -- and a logistical challenge of staggering proportions -- is held in the northern city of Prayagraj in Uttar Pradesh state.

Organisers are expecting 400 million people at the festival, which began on Monday and runs until February 26.

Here are snapshots of some of those taking part in the world's largest gathering of humanity.

- The AI Student -

Studying artificial intelligence engineering at a private college in New Delhi, 18-year-old Rishabh Kumar Singh lied to his teacher to attend the festival, saying he was unwell.

But Singh said his mother approved of the trip -- and got her husband to sponsor it.

"I got my devotional streak from her," he said.

"As a child, she would take me along to all kinds of religious ceremonies."

Singh took an overnight train from the capital to arrive in time for the first day of the fair.

After taking a dip in the sacred waters on Monday, his next stop is to meet the naked ash-smeared ascetics known as Naga sadhus, who attend the fair.

Having already skipped classes, Singh will then make detours to the Hindu holy cities of Varanasi and Ayodhya before returning to study.

- The Cave-dwelling Monk -

Dressed in saffron robes, the trident-wielding monk calls himself Jogiraj Giri Phalhari Tyagi Naga Baba –- Phalhari being a reference to his fruits-only diet.

The 63-year-old said he has lived alone in a deep cave inside a tiger reserve in central India for 40 years.

"For 14 years and seven months I have only had fruits -- and no grains at all," he said.

He was at the fair to "enjoy the festivities" and pay his "respects to the gods".

The ascetic said he would stay for the whole six weeks of the fair, camping in the quarters of the Juna Akhara monastic order that he has been part of for the last 25 years.

He is impressed by the logistical arrangements, which include around 150,000 toilets and a network of community kitchens, each able to feed up to 50,000 people.

The credit, he believes, is due to India's Hindu nationalist Prime Minister Narendra Modi.

"Under him, India is becoming a country where our ancient culture is respected," he said.

"Our civilisational glory is being restored."

- The Repeat Pilgrim -

It is the second time at the Kumbh Mela for 40-year-old Shyamlal Shrivastava from Madhya Pradesh state, who last attended the fair in 2012.

But the property agent subsequently lost his left leg when he slipped trying to board a train, and that has made this Kumbh Mela a very different experience.

Traversing long distances over the muddy floodplains of the largely vehicle-free fair on his walker is difficult.

But Shrivastava says he will do what it takes to ensure his "all-important bath" in the holy waters.

Shrivastava however does not blame his misfortune on divine design.

"God can never do anything wrong," he said. "If I get upset with the almighty, I will have nothing to hold on to."

- The Science Teacher -

A school science teacher in the western state of Rajasthan, Meenakshi Gautam is enthusiastic about bathing at the Sangam, the holy site where the Ganges, Yamuna and mythical Saraswati rivers meet.

"My life's purpose will be fulfilled when I take the dip," said the 38-year-old, travelling with her husband.

Having visited almost all other key Hindu pilgrimage sites, Gautam said she was determined to attend the Kumbh Mela.

"It is at the centre of global attraction right now," she said. "And it seems even bigger than I had imagined, I am enjoying it so much."

- The Housewife and Friends -

The homemaker from the eastern Indian state of West Bengal planned the trip two months ago with a group of friends.

"The husband is home," said 56-year-old Chandana Sarkar with a smile.

The large crowds, she insisted, were not intimidating. Things had been smooth despite no one in the group speaking Hindi, the dominant language in northern India.

"It is such a nice experience," she said. "We love it."

It was their first trip together and the women were happy, said Sarkar, who is staying in the vast tent city along the riverbanks.

"I thought I would be very cold while bathing," she said. "But once you are inside you don't even feel it."

G.Miller--SFF