This Mahamaham festival occurs when the sun is in the Zodiacal sign of Aquarius (Khumbha), Jupiter transits Leo (Simha) and the moon is in conjunction with the constellation Maham. Generally all the these astronomical combination take place on a full moon day of the Tamil Month of Masi (Solar Kumbha Month) i.e. either in the latter half of February or in the first half of March. The festival comes off once in twelve years. Mahamaham bathing festival is concentrated on a single day, the concourse of pilgrims being all the more. The festival at Haridwar, Allahabad, Nasik and those in Andhra Pradesh happen to be bathing in river while the Mahamaham is bathing in a tank, generally followed or preceded by a dip in the River Kaveri at Kumbakonam. The Mahamaham tank, trapezoidal, (looking rectangular) in shape covers roughly an area of about five acres and a half with a full capacity depth of ten feet. Every year there is smaller festival, but during big one as many as 2 million people gather.