Kumbh 2019 at Sangam City, Prayagraj, is a celebration of an ancient tradition: a dip in the holy waters where the mythical Saraswati meets the majestic Ganga flowing from the Himalaya and the sacred Yamuna, believed to have originated in the netherworld. The time of its celebration, far from being arbitrary, is based on a complex astrological calculation where the alignment of the stars determines the time and place of the Kumbh in one of the following four river-sites: Haridwar, Prayagraj, Nasik, and Ujjain. These riverside festivals and the city that springs up around them are attended by millions, making the Kumbha Mela the largest religious gathering, perhaps the oldest, and the largest temporary city in the world.