Many people are not familiar with Kumbh Mela, and yet it is the largest celebration on earth: depending on the positions of Jupiter, the sun and the moon, Hindus travel to certain places along holy rivers, the Ganges for example, to bathe and cleanse themselves of sin. With a 2013 attendance of approximately 34 million, the triennial pilgrimage requires that the communities hosting the gatherings create functioning temporary structures to transport,...