Indian yoga guru Swami Ramdev (centre) taking a dip at the Sangam, the confluence of the rivers Ganges, Yamuna and Saraswati, during the 45-day Ardh Kumbh Mela in Allahabad, January 11.

Millions of Hindu pilgrims braved bitter cold and security concerns to gather on the banks of the holy Ganges river for a mass ritual believed to wash away their sins.

Photograph: AFP/Getty Images