The Rajagopalaswamy Temple is the reason Mannargudi exists. This sprawling Vaishnavite complex, spread over 23 acres, is one of the largest Krishna temples in South India and one of the 108 Divya Desams — the sacred sites celebrated by the Alvar poet-saints. The main gopuram rises to about 60 metres and is visible from well outside town, a landmark in the flat delta landscape.
Inside, the temple is organised around several prakarams (concentric enclosures). The innermost shrine houses the main deity, Sri Rajagopalaswamy, depicted as Krishna with cows. The Haridra Nadhi, a large rectangular temple tank, sits within the complex and is used for float festivals during Brahmotsavam. The tank is one of the largest in Tamil Nadu and worth seeing in its own right, especially in the early morning when the gopuram reflects off the water.
The temple is busiest during the Panguni Brahmotsavam (March-April), a 10-day festival that draws tens of thousands of pilgrims. On the Garuda Sevai day, the processional deity rides a massive wooden Garuda mount through the streets. The temple is open daily from about 6am to noon and 4pm to 8:30pm, and non-Hindus can enter the outer prakarams freely.