The Kasi Viswanathar Temple sits directly on the south bank of the Mahamaham tank and is one of the most photographed of the temples around it. Dedicated to Shiva in the form he is worshipped at Varanasi (Kasi), the temple has a distinctive set of nine shrines for the Navakanniyars — personifications of the nine sacred rivers of India said to gather in the tank at the Mahamaham festival.
It is small by Kumbakonam standards, but it is integral to the ritual circuit around the tank. On Mahamaham day, the procession of deities from the major temples ends here.