In the northern Indian city of Allahabad, in a place where three sacred rivers come together, Hindu devotees gather every year in the early winter morning to take a holy dip in the chilly waters.

The Magh Mela festival is an annual religious event, when thousands of devotees take a dip in the waters of Sangam, the confluence of the rivers Ganges, Yamuna and the mythical Saraswati.

The festival takes place each year in the month of Magh, as dictated by the Hindu astrological calendar.

This year, the festival began on Jan 15 and will continue until March 7. The length of the festival fluctuates between 40 and 50 days.

Every 12 years, Magh Mela at Allahabad is celebrated as an even bigger festival - the Kumbh Mela.

And once every 144 years, there is a Maha Kumbh Mela.

The bigger festivals attract millions of bathers as they are considered even more important.

During the last Maha Kumbh Mela, in 2013, an estimated 100 million Hindus attended the festival.