PRAYAGRAJ, India — Tens of thousands of naked Hindu ascetics and millions of pilgrims took dips in freezing water at the confluence of sacred rivers in northern India on Tuesday, in the first of a series of major baths in the Maha Kumbh festival, the largest religious congregation on Earth.

Millions of devotees have gathered in the northern Indian city of Prayagraj, Uttar Pradesh, as the Mahakumbh Mela, the world’s largest religious festival, officially begins. The six-week-long festival draws Hindus from across India and the globe to Sangam,