The times of the Kumbh Mela are set by where Jupiter, the Sun, and the Moon are in the zodiac. The sacred rivers are thought to have a quality similar to cosmic nectar.
The Kumbh Mela, a Hindu festival, is held annually in Haridwar, Prayagraj, Ujjain, and Nashik, completing a full cycle every 12 years.
The 2013 Kumbh Mela was a massive economic event which generated around 12,000 crore in revenue and created 650,000 jobs.
Kumbh Mela of 2013 was held in Prayagraj which attracted over 10 crore people, making it the "biggest gathering on Earth."
The kumbh attracts Various Hindu groups, like the Kalpwasis, who bathe every day, the Urdhwavahurs, who follow strict austerities, and the Nagas, who abstain from clothing, are drawn to the celebration.
The 2013 mela had 14 temporary hospitals with 243 doctors, over 40,000 bathrooms, and 50,000 police officers to keep order.
According to Hindu mythology, the kumbh mela is believed to be the place where immortality nectar was thrown at four spots during a god-demon fight, making rivers sacred.