Kumbh Mela is one of the largest religious gathering on earth and one of the most important Indian pilgrimage. Attended by millions of pilgrims, devotees and holy men/women irrespective of barriers of caste, creed, region, it is known as the most important pilgrimage gathering around the world.

This religious festival is celebrated four times every twelve years, the site of the observance rotating between four pilgrimage holy cities on four sacred rivers: at Haridwar (Uttarakand) on the Ganges River, at Ujjain (Madhya Pradesh) on the Shipra, at Nasik (Maharastra) on the Godavari, and at Allahabad/Prayag (Uttar Pradesh) at the confluence of the Ganges, Jamuna, and the mythical Sarasvati. The 2011 Kumbh Mela was the largest gathering of people with over 75 million pilgrims. The gathering was so huge that the crowd was visible from space.

Source: http://www.actupondy.com/en/past-cultural-events-pondy/exhibitions/10870-kumbh-mela-exhibition-2011, https://www.scoopwhoop.com/inothernews/interesting-india/#.4zs043cfr