India readies for 400 million pilgrims at mammoth festival

Beside India's holy rivers, a makeshift city is being built for a Hindu religious festival expected to be so vast it will be seen from space, the largest gathering in history.

Line after line of pontoon bridges span the rivers at Prayagraj, as Indian authorities prepare for 400 million pilgrims -- more than the combined population of the United States and Canada -- during the six-week-long Kumbh Mela.

The millennia-old sacred show of religious piety and ritual bathing is held once every 12 years at the site where the holy Ganges, Yamuna and the mythical Saraswati rivers meet.

But this edition from January 13 to February 26 is expected to be a mega draw, as it is set to coincide with a special alignment of the planets.