This temple engrosses an area of 15 acres and it has vast Prakarams, towering sanctum sanctorum, and several mandapams. The fort like walls which surround the outermost prakaram are pierced with four entry towers. This temple was built by Gandaraditya Chola son of Parantaka Chola I. The inner mandapams and the outer mandapams were built by Sekkeezhaar and Govinda Deekshitar who was the Minister of Achyutappa Nayakar. There is an image of Sekkizhaar and a mandapam built by him, here as well. There is a shrine to Raahu in one of the prakarams. The Piraiani Nudalaal Ambaal shrine is situated in the inner mandapam near the Naganathar shrine, while the Girikuchambika shrine is housed in a separate sanctum. Reigning dieties of the temple are Nageswarar, Naganathar, Sambu Karanyeswarar, Pirainuthalanai Amman, Girikujambal (Kunramamulaiamman).

Devas and Asuras churned the Paarkadal to obtain Amirtham (Nectar) that which would free from death, and alive for ever. When the Amirtham came out, Lord Vishnu in the guise of Mohini was distributing the Amirtham only to Devas. Lord Vishnu worried about that the evil deeds of the will increase multifold if Asuras consumed the nectar. Realising this reason, one of the Asuras took the form of a Deva with the help of Asura guru Sukrachariya and consumed the nectar.

Suryan and Chandran complained to Lord Vishnu as they have noticed that. Lord Vishnu came to know that and hit the Asura on the head in anger with the spoon in his hand. The head was cut off and fall down on the ground. The body portion was thrown away fell in Pothigai mountain region when the head portion joined with a snake body and became Rahu Bhagavan. The body of that Asura was preserved by a Brahmin which grew, because of having drunk the nectar. This body was attached to a snake's head and became Kethu Bhagavan.

Since Rahu is a serpent (Naga), the main deity is Naganatha Swamy and this place is named Thirunageswaram. In this shrine, Rahu is accompanied by his consorts Naga Valli and Naga Kanni. When Abhishekam is performed to Rahu during the Rahu Kaalam, the milk when it falls on the body turns blue, and again turns to white when it leaves the idol.

Tirunageswaram is considered to be the 29th in the series of Tevara Stalams in the Chola kingdom located south of the river Kaveri. Offering worship at Kudanthai Keezhkottam (Nageswarar Temple) in the morning, at Tirunageswaram at noon and at Tiruppampuram in the evening on a given day is considered to be of special significance. Apar, Sambandhar and Sekeezhar have sung hymns in praise of this shrine. There are as many as 12 Theerthams here.

Legend has it that the mythological serpents Adiseshan, Kakkan Karkodagan, Sounagar, Suryan, Vinayagar, Gautamar, Nalan, Parasarar, Pandavas, Vasishtar, Indran, Brahma, Bageerathan, Chandrasenan, Nargunan are said to have worshiped the temple Siva here and got grace. Legend also has it that Nala worshipped Shiva here as in Tirunallaar. Gowtama muni, Paraasarar and Bhageerata are also associated with legends related to this temple.

The shrine dedicated to Rahu is at Thirunageswaram, 7 Kms from Kumbakonam, and only about 2 Kms from Uppiliappan Kovil. This Shivastalam is a vast temple known for its shrine to Raahu, one of the nine celestial bodies. According to the legend Rahu and Kethu are associated with the legend of the churning of the milky ocean.

The annual Bhramotsavam is observed in the month of Kartikai while the Sekkizhaar festival is celebrated in the month of Vaikasi.