Vast crowds of Hindu pilgrims in India bathed in sacred waters as the Kumbh Mela festival opened on Monday, with organisers expecting 400 million people — the world’s largest gathering of humanity — to assemble over six weeks. The millennia-old Kumbh Mela, a show of religious piety and ritual bathing — and a logistical challenge of staggering proportions — is held at the site where the Ganges, Yamuna and mythical Saraswati rivers meet. “I feel great joy,” said Surmila Devi, 45, after bathing just before dawn. “For me, it’s like bathing in nectar.” Businesswoman Reena Rai’s voice quivered with excitement as she spoke about the “religious reasons” that brought her to join the sprawling tents, packed along the river banks in the north Indian city of Prayagraj in Uttar Pradesh state. “As a Hindu, this is an unmissable occasion,” said the 38-year-old, who travelled around 1,000 kilometres (620 miles) from Madhya Pradesh state to take part in the festival, which runs until February 26. Saffron-robed monks and naked, ash-smeared ascetics, many of whom had walked for weeks to reach the site, roamed the crowds offering blessings.