The festival has its roots in a Hindu tradition that says the god Vishnu wrested from demons a golden pot containing the nectar of immortality.
In a 12-day fight for possession, four drops fell to earth, in the cities of Allahabad, Haridwar, Ujain and Nasik. Every three years a Kumbh Mela is held at one of these spots, with the festival at Allahabad the holiest of them all.
Once every 12 years, tens of millions of pilgrims stream to the small northern city of Allahabad from across India for the Maha Kumbh Mela, or Grand Pitcher Festival, at the point where the Ganges and Yamuna rivers meet with a third, mythical river.
Officials believe that over the next two months as many as 100 million people will pass through the temporary city that covers an area larger than Athens on a wide sandy river bank. That would make it larger even than previous festivals.