Kumbh is held at four places: Haridwar, Nashik, Prayag (Allahabad), Ujjain in every six, twelve and 144 years. Kumbh Mela is celebrated at different locations depending on the position of the planet of Bṛhaspati (Jupiter) and the Sun.
Jupiter and Sun both in Leo — Nashik
Sun in Aries — Haridwar
Jupiter in Taurus and Sun in Capricorn — Prayag(Allahabad)
Jupiter and Sun both in Scorpio — Ujjain