The Maha Kumbh Mela ("great festival of the pot of nectar of immortality") is held every three years in each of four different locations, returning to each of four places every twelve years. An Ardh (half) Mela (festival) takes place six years after the Maha Kumbh in each location.
Afraid of getting lost. Prayag
During the Ardh Khumbh Mela, a lot of pilgrims are afraid of getting lost in the crowd. So a lot do this. They hang up to the people in front of them. Sometime you can watch little trains from the same family.