Until 10 March, the Maha Kumb Mela in Allahabad will see some 100 million Hindu pilgrims cleansing their sins at the confluence of the Ganges, Yamuna and mythical Sarasvati Rivers.

It has been 144 years in the making, but India’s Maha Kumbh Mela is finally here.

The Maha Kumbh Mela, a mass Hindu pilgrimage, has been taking place for thousands of years, with its origins in Hindu mythology. In Hindu creation myths, the gods and demons fought over a kumbh (pitcher) containing the nectar of immortality, but during the fight four drops of the liquid fell to earth, one at Allahabad in Uttar Pradesh, one at Hardiwar in Uttarakhand, one at Ujjian in Madhya Pradesh and one at Nashik in Maharashtra.

Today, a Kumbh Mela is held roughly once every twelve years in Hardiwar, Ujjian and Nashik. The one in Allahabad, which is also held every twelve years, is the most important and largest, and this is called a Maha (or great) Kumbh Mela. Thanks to an unusual alignment of the planets, this year’s event is even more auspicious than normal. In fact, the last time there was one this important was 144 years ago and the next will not be until around 2157. Pilgrims believe that by attending the festival and bathing in the waters of the rivers that run through Allahabad or the other host cities, they will cleanse away their sins and bring salvation.

When we say the Maha Kumbh Mela is big, we really mean big. The last Kumbh Mela, held in Hardiwar in 2010, was attended by an estimated 40 to 70 million pilgrims. But for this year’s event, running until 10 March, Allahabad authorities estimate that some 100 million pilgrims will pour into the city of 1.2 million inhabitants to take a dip at the confluence of the Ganges, Yamuna and mythical Sarasvati Rivers. Although people bathe every day throughout the festival, there are three especially holy days when bathing brings even greater merit. The most auspicious of these is on 10 February, when up to 35 million people are expected to dip in the sacred waters.

The Kumbh Mela brings together Hindus of all castes and creeds, but its most famous attendees are the sadhus (wandering Hindu holy men who have renounced caste, money, possessions and social position). On each of the main bathing days they lead the dawn charge to the river, but always at the very front come the nagas (sadhus who have renounced virtually everything, including clothing).

The Maha Kumbh Mela got off to an awe-inspiring start on Monday, with the first of the main bathing days seeing an estimated 10 million taking a dip. However, if you want to attend, you will need to be quick. The authorities have set up tented camps along the banks of the Ganges and Yamuna rivers, but with about 100 million people attending, demand for accommodation is very high.