The Festival of the Great Tank
Mahāmakham (Sanskrit/Tamil: mahā = great + makham = sacrifice/festival; 'the great festival sacrifice') is the major 12-yearly festival at Kumbakonam in Tamil Nadu's Tanjore district, where the Mahāmakha tank is believed to receive the combined waters of all sacred rivers at the auspicious moment of a specific planetary alignment.
The Sacred Convergence
According to tradition, at the Mahāmakham moment (when Jupiter is in Leo and the Sun and Moon are in Aquarius), all the sacred rivers — Gaṅgā, Yamunā, Sarasvatī, Kāverī, and others — flow invisibly into the Mahāmakha tank. Bathing in the tank at this moment is believed to confer the merit of bathing in all sacred rivers simultaneously.
Sri Vaishnava Significance
Surrounding the Mahāmakha tank are twelve Śiva temples and one Viṣṇu temple (Ādi Kumbheśvara). For Śrī Vaiṣṇavas, the Kumbhakonam region is also significant for the Sarangapani and Chakrapāṇi Divya Deśams nearby. The Mahāmakham festival draws pilgrims from the entire Tamil-speaking world.