The Kumbh Mela festival, the largest religious gathering in the world, has begun in the northern Indian city of Prayagraj.

Over the coming 45 days, an estimated 400 million Hindus are expected to come together for Maha Kumbh Mela. The festival is held every 12 years but the "Maha" or grand Kumbh Mela takes place only every 144 years, "marking the 12th Kumbh Mela and a special celestial alignment of the sun, moon and Jupiter", said The Guardian.

Millions of Hindus have arrived at Prayagraj in the northern Indian state of Uttar Pradesh for the Maha Kumbh Mela, touted as one of the largest religious gatherings in the world. Over the next three weeks,