14 January 2013
Last updated at 15:15 ET
India's Kumbh Mela is under way. Major versions of the festival are held every 12 years and this is thought to be the world's largest gathering of humanity.
Millions of people arrived for the first day of the festival, in Allahabad, which is expected to attract more than 100 million people over the next 55 days.
Hindus believe a dip at the confluence of the Ganges and Yamuna rivers in Allahabad, called Sangam, will cleanse sins and help bring salvation.
The festival started at dawn, led by naked ash-smeared Hindu holy men - Naga sadhus - with marigold garlands around their necks.
The sadhus arrived in a colourful procession and sprinted into the chilly waters of the Sangam.
Ordinary men and women followed the sadhus into the water - many had come from all parts of this vast country to take part.
Millions of pilgrims are expected to flock to the holy river during the next eight weeks - at its peak, authorities expect nearly 30 million people to be on the site.
Allahabad has been preparing for the festival for months, and 14 temporary hospitals and 40,000 toilets have been built to cope with the millions of pilgrims.
Teams are managing crowds on the river bank, encouraging pilgrims who have finished bathing to move away and make space for others.
Several squads of police on horseback regulated the flow of pilgrims to and from the waters. Some 50,000 have been deployed to keep order during the festival.