Kumbh Mela is a mass Hindu pilgrimage of faith in which Hindus gather to bathe in a sacred river. It is considered to be the largest peaceful gathering in the world where around 100 million people were expected to visit during the Maha Kumbh Mela in 2013 in Allahabad.

It is held every third year at one of the four places by rotation: Haridwar, Allahabad (Prayaga), Nashik and Ujjain. Thus the Kumbh Mela is held at each of these four places every twelfth year. Ardha (“Half”) Kumbh Mela is held at only two places, Haridwar and Allahabad, every sixth year. The rivers at these four places are: the Ganges (Ganga) at Haridwar, the confluence (Sangam) of the Ganges and the Yamuna and the mythical Saraswati at Allahabad, the Godawari at Nashik, and the Shipra at Ujjain.

The name Kumbh Mela comes from Hindi, and in the original Sanskrit and other Indian languages it is more often known as Kumbha Mela. Kumbha means a pitcher and Mela means fair in Sanskrit. The pilgrimage is held for about one and a half months at each of these four places where it is believed in Hinduism that drops of nectar fell from the kumbha carried by gods after the sea was churned. Bathing in these rivers is thought to cleanse one of all sins. The festival is billed as the “world’s largest congregation of religious pilgrims”.

Mauni Amavasya traditionally attracted the largest crowds at the mela, held here every 12 years. The current Kumbh Mela was held on 14 January 2013 at Allahabad. The day marked the second and the biggest Shahi Snanam (royal bath) of this event, with 13 akharas taking to the Sangam. 10 Feb 2013 was the biggest bathing day at the Maha Kumbh Mela and probably the largest human gathering on a single day. Over 30 million devotees and ascetics took holy dip on the occasion of Mauni Amavasya.

Source: http://en.wikipedia.org/wiki/Kumbh_Mela