The world's largest religious assembly is called Kumbh Mela. It is held in four Indian cities every three years: Prayagraj (formerly Allahabad), Haridwar, Nashik, and Ujjain. Millions of Hindus from all over the world congregate to these sites during this occasion in an effort to atone for their sins by taking a ceremonial dip in the holy water. Many tents are erected along the riverbanks to house the pilgrims during this momentous spiritual assembly.