Saints read royal decree and participated in a ritual bath ahead of the 'Maha Kumbh Mela' in Allahabad on Sunday.
The eight-week-long festival is beginning from Monday, in which thousands of devotees will bathe at the Sangam -- the confluence of the Ganges, the Yamuna and the mythical Saraswati rivers.
Madhuchakha Vashanj, a priest, said that the royal bath is an age-old tradition and it is believed that it washes away all sins and cycle of rebirth ends.
"This is an age-old tradition and we participate in the Shahi Snan (Royal Bath). Royal kings would take a bath and before that, the learned saints would bathe the kings. So, the tradition has been continuing for years and saints continue to take the royal bath," he said.
Processions of hundreds of Sadhus (sages) arriving at their camps or heading to the bathing area, often accompanied by elephants, camels and drummers, is a big tourist draw.
Around 12 temporary iron pontoon bridges have been built over the Ganges and Yamuna rivers to allow these processions to take place.
Hindus believe that bathing in the Ganges during the 56-day festival cleanses them of their sins.
The festival, which dates back thousands of years, is celebrated once every 12 years, with lesser festivals held at stages in between.
In 2001, more than 40 million people gathered on the main bathing day in Allahabad, breaking a world record for the biggest human gathering.
The authorities, who have constructed a vast tented city at the festival ground for masses of pilgrims, say numbers are expected to be 20 percent higher than the previous ocassion.
The state government has spent millions to provide everything from sanitation to security.
Officials say 50 power sub stations have been built, while around 10,000 police personnel will be deployed to maintain order.
The festival will end on March 10.