Millions of devotees began bathing at the confluence of the holy rivers Ganges, Yamuna and Saraswati, as the world's largest human gathering gets under way at Prayagraj in the northern Indian state of Uttar Pradesh on Tuesday. Over an eight-week period, about 150 million people will participate in the Kumbh Mela, which would make this year's gathering the most crowded in its history. To cope with the influx of visitors, the civic authorities have built hundreds of temporary bridges, mass kitchens and more than 100,000 portable toilets. The Hindu festival may be religious, but it is also a mix of spirituality and tourism. Officials are expecting more than a million people from outside India to attend this year. The Kumbh Mela finds its origins in the Hindu mythology, according to which, a few drops of the "nectar of immortality" fell on earth from heaven – all the places that host the festival. Devotees believe dipping in the holy rivers will cleanse them of their sins and help attain "moksha", or salvation, from the cycle of life and death. Check out some of the best photos so far below: