'Kumbh' in sanskrit refers to 'pot or pitcher' and 'mela' is 'festival'. Kumbha Mela, thus finds a meaning as a festival of the pot. The historic origin of the Kumbh Mela dates back to the vedic times. It is believed that once the gods(devtas) were cursed by Rishi Durvasa. This made them lose their powers, thus weakening their body and mind. To regain their old strength and vigor, the devtas planned to churn the primal ocean to extract the 'elixir of immortality', the 'amrit' or 'the water of life'. They approached demons (daityas) and persuaded them to perform 'Samudra Manthan' (churning of the ocean) to bring out the nectar. One who would drink the nectar would become immortal and therefore, most powerful and indestructible. Thus, gods and demons agreed to share the nectar once it was brought up from the depths of the ocean. Have you been to Kumbh mela ever?
The pilgrimage occurs four times every twelve years, once at each of the four locations. Each twelve-year cycle includes the Maha (great) Kumbha Mela at Prayag, attended by millions of people, making it the largest pilgrimage gathering around the world. Maha Kumbha Mela is held in Allahabad every 12 years. It also takes place in three other holy places in India every 12 years— Haridwar, Ujjain and Nasik. The time for Kumbha-mela is judged by the astrological positions of Jupiter and the Sun. In Prayag (Allahabad) the Kumbha-mela takes place during January-February, when Jupiter is in Taurus and the Sun enters Capricorn. The Kumbha-mela in Prayag (Allahabad) is considered especially auspicious. This very interesting event draws about 15 million people and is the largest attended event in the world.
I have been there, that's a huge crowd and you really have lots of fun. The Last Spell: Seeing Dhanvantari with the pot of nectar, the gods and demons became anxious. The demons who were physically stronger than the gods forcibly seized the pot. The demons and the Gods fought over the pot for twelve days and twelve nights (equivalent to twelve human years). Finally, Lord Vishnu, disguising himself as an enchantress, took the pot of nectar from the demons and passed to Jayant, Lord Indra's son, who assumed the form of a large bird, flew off with the jar. Some drops of the nectar fell on his way at four places: Allahabad, Haridwar, Trimbakeshwar and Ujjain. Each of these places became the holy pilgrimage sites for Kumbh Mela.
