Naga Sadhus — the naked ascetics dipping into icy waters

The Maha Kumbh Mela draws many Hindu ascetics and saints, including the Naga Sadhus. These saints are a prominent sight at the mela, as they come naked and smeared in ash, sporting dreadlocks and wearing jewelry made from "rudraksha," a naturally occurring dry fruit.

With chilly temperatures in Prayagraj, many devotees shiver to take the holy dip in the waters. But Naga Sadhus seem comfortable and rarely show signs of feeling cold.

It is believed that they are able to regulate their body temperature through yoga and breathing techniques. The ash used to cover their bodies also helps protect them from the cold.

What is the Maha Kumbh Mela

The Maha Kumbh Mela is the largest gathering of humanity, with over 400 million people expected to attend — which is more or less equivalent to the combined population of the US and Canada.

The festival takes place over a period of 45 days, in several locations along major rivers in central and northern India.

"Maha" stands for great or grand, and "Kumbh" literally means pot. The festival is rooted in the Hindu myth of a battle between gods and demons over a pot containing the elixir of immortality.

As the story goes, a few drops of the elixir spilled over in Prayagraj, Haridwar, Ujjain and Nasik, where the festival is held once every 12 years. Prayagraj always tends to draw the biggest crowds.

An "ardh," or half Kumbh, is celebrated at the halfway mark between the two festivals.

During the festival, devotees gather at the confluence of the rivers Ganges, Yamuna and Saraswati to take a holy dip in the water. Devotees believe this will absolve them of sins and grant them "moksha" or salvation.

The key bathing ritual days, "shahi snan," occur on January 14, January 29 and February 3.