Naga Sadhus, naked Hindu holy men, walk in procession after having bathed on the banks of Sangam, the confluence of the holy rivers Ganges, Yamuna and the mythical Saraswati. (Photo by Daniel Berehulak/Getty Images)

The city of Prayagraj will host Kumbh Mela, the largest gathering of humanity, in January 2019 and it promises to be a grand spiritual affair.

Kumbh Mela 2019 will commence on January 15 and end on March 31. The Uttar Pradesh government expects around 100 million to 150 million people, including one million foreign tourists, to visit the state during this time.

Here are five interesting facts about Kumb Mela:

The Kumbh Mela is held every three years and switches between four different locations – Haridwar, Prayag, Ujjain and Nasik.

Foreigners from various countries take part in an environmental awareness parade at Sangam, the confluence of the rivers Ganges and Yamuna and mythical Saraswati, during the Maha Kumbh Mela in Allahabad. (Sanjay Kanojia/AFP/Getty Images)

The first written document that describes the Kumbh Mela was recorded by Huan Tsang- a Chinese visitor who visited India in the seventh century.

Hindu devotees arrive at the banks of the river Ganges to take a bath during the Kumbh Mela festival in Haridwar.

Holy men from different sects of Hindu religion such as the Nagas Sannyasi, Kalpwasis, Shirshasinse, Parivajakash, and Urdhawavahurs throng the Kumbh Mela.

Hindu devotees bathing (Photo by Allison Joyce/Getty Images)

Millions will undergo a self-purification dip at the confluence of the Ganga, Yamuna and Saraswati rivers. It’s believed that anyone who dips in the triveni sangam will be purified of their sins and be free from the cycle of rebirth.

Hindu devotees bathe on the banks of Sangam (Photo by Daniel Berehulak/Getty Images)

Special facilities such as temporary toilets and hospitals are set up to cater to the needs of visitors who gather to celebrate the Kumbh Mela.