The story of this temple dates back to 7th century during Pallava reign. There was a Shiva devotee living in this place during 7th century called Poosalaar. who had a desire to build a temple for Lord Shiva at this place unfortunately he could not find funds for the same. Poosalaar finally decided to build a temple for the Lord by himself, As he was well read and knew all the Aagama Vidhis and nuances to build a temple, he wanted to start building the temple.in his mind
He sat under a tree called Iluppai and started meditating. He planned each and every small detail to perfection for the construction of this temple in his mind itself. He also marked an auspicious day to commence the holy work. The temple work progressed in his mind. He built the temple step by step. He had designed evebything in his mind right from Vimana, Sanctum, Temple Pond, Compound walls etc., and executed each in detail as per what he had in mind.
After the temple construction work came to a finish. He even had organised all the utensils required for the temple. Finally, he also fixed an auspicious date for Kumbhabishekam (consecration) of the temple. He prayed to Lord Shiva to be present for the consecration and offer His blessings.
During the same period, a Pallava king called Rajasimha was ruling this part, with his capital as Kaanchi (today’s Kanchipuram). He also was a sincere devotee of Lord Shiva and was building a huge beautiful temple for the Lord, at Kaanchi. He named the God as Kailasanathar and the temple as Rajasimmeswaram. The king was too proud to see the grandeur of the temple constructed by him.
The king also marked a date for consecration, while the finishing touches were going on at the temple. Lord Shiva appeared in his dream and told him that He cannot make it to the consecration of the king’s temple on the said date and asked him to change the day of consecration, as He had to be present for consecration of another temple built by Poosalaar of Thiruninravur.
The king woke up shocked . He wanted to know about the temple which God informed him of. He immediately started with his queen, ministers to see Poosalaar’s temple at Thiruninravur.
He came to Thiruninravur the next day and enquired with many people about a new Shiva temple built by Poosalaar. Nobody knew anything about the temple but directed the king to the place where Poosalaar was meditating under the Iluppai tree.
King went and asked Poosalaar himself about the temple. Poosalaar, on hearing the king explaining about his dream, was overwhelmed to realize the mercy shown to him by Lord Shiva. Poosalaar explained to the king that he had been constructing the temple in his heart (Manasu in Thamizh) and had fixed a date for consecration.
Poosalaar made the king to look at his heart and realize the temple which he constructed. King was able to see and realize the temple made by Poosalaar.
Knowing this Rajasimma was amazed to see the devotion and sincerity of Poosalaar. The king himself took all the specifications of the temple which Poosalaar had in mind and physically constructed a temple for the Lord here. This temple is also called Manakkoil.As Poosalaar originally built the temple for the Lord in his Hridayam, the Lord here is known as Hridhayaaleeswarar.
The main deity here is called Sri Hridhayaaleeswarar. The Goddess here is Sri Maragadhaambigai
The main sanctum has an east facing Sivalingam with entrance from the south side. There is an image of Poosalar worshipping the Sivalingam inside the main sannidhi.
The Maragadambigai sannidhi faces south and has a petite amman in standing posture. The sanctum has a gaja prushti vimanam with Lingothbhavar, Brahma Dakshinamurthy and Durga in various niches.The entire complex is tastefully covered allowing for natural sunlight to illuminate these gods without the harshness of scorching sun!!.
There are a lot of Murals painted on the roof of the mandabam on the east side
(Various figures on the right side of the main entrance)
There is also a statue of King Rajasimmam in the main complex.