The world's largest gathering of people, the 55-day congregation known as Kumbh Mela, has begun with tens of thousands of devotees, led by ash-smeared Naga ascetics, taking a dip at the confluence of the three most sacred rivers in the north Indian town of Allahabad.
ITV News Correspondent Geraint Vincent reports:
The festival started at the crack of dawn today when Hindu saints started coming in heavily decked-out chariots, some in silver and gold, with hundreds following in a procession on foot, beating drums and blowing conch shells.
The inaugural day of the two-month-long congregation, often described as the "greatest show on earth", was marked by the first "Shahi Snan" of 13 "akharas".
Naga Sadhus - a martial order of ascetics who move about either naked or scantily clad with matted hair and ash smeared bodies - marched to a main bathing area at Sangam in processions with their leaders perched atop ornately decorated elephants, horses and chariots and musical bands in a unique blend of austerity and opulence.
The Mela will see up to 100 million Hindus assembling over the next two months to take a holy bath in the Ganges, which is believed to cleanse one of all sins.
For many Hindus, the Kumbh Mela is a religious vacation, where prayers are offered and sought while camping together with families and friends at the carnival site for the entire mela period.
The Kumbh Mela takes place every 12 years in the holy city of Allahabad with smaller events taking place every three years in other locations around the country.
According to Hindu mythology, the mela originated after a few drops of nectar of immortality fell on Allahabad, Nasik, Ujjain and Haridwar, the four holy places that host the festival alternately.
The different sects of Hindu saints are given their turn to avoid violent clashes among ascetics.
The sects, known as akharas, have been allotted fixed time, ranging from 30 minutes to about an hour depending upon the size of their respective procession, for bathing.
The routes for going to and returning from Sangam are separated, so as to ward off the possibility of members of rival akharas coming into contact with each other.
As soon as pilgrims finish bathing, they are encouraged to move away and make space for other bathers to avoid a stampede.
There are six particularly auspicious days to bathe, also known as Royal Bathing days.
The biggest bathing day is going to be on February 10, when approximately 305 million people are expected to take to the waters.
Holy men, seers and saints from across the nation have assembled at Allahabad for the two-month spectacle which offers a glimpse of Indian spiritualism.
Local officials have made elaborate arrangements for devotees who will be flocking to the city.
More than two million pilgrims are already living for the entire mela period in make-shift accommodation on the banks of Ganges.
Most of them are staying in tents, temporary shelters or with their gurus.
The large gathering is also a business opportunity for the local government. According to an Indian trade body, the festival is expected to generate at least £1.3 billion worth of business.