Tens of thousands of Hindus seeking absolution of their sins immersed themselves on Monday in freezing waters at the confluence of sacred rivers, as India began a six-week festival expected to draw the world's largest gathering of humanity.

Held every 12 years, 2025's Maha Kumbh mela has seen the construction of 400km of temporary roads, a 10,000-acre pop-up tent city, 150,000 toilets, three hospitals and more.

The Maha Kumbh Mela, or the Great Pitcher Festival, will bring more than 400 million people to Prayagraj city in northern India over a period of six weeks starting Monday, making it the largest gathering of humanity in the world.

India set for Hindu festival Maha Kumbh Mela | REUTERS WARNING: May contain nudity The Maha Kumbh Mela, the world’s largest gathering of humanity, begins in the northern Indian city of Prayagraj, with millions of devout Hindus arriving to take a dip in the holy river Ganga.