Thirumukkoodal is a village located about 20 kms from Kanchipuram on the road going towards Chengalpattu. While going from Chengalpattu, one can reach Pazhaya Seevaram, 5 kms before Walajabad. From Pazhaya Seevaram one has to take left and cross the bridge on the river Palar to reach Thirumukkudal. Thirumukkoodal has an ancient temple for Lord Vishnu called ‘Sri Appan Prasanna Venkatesa Perumal’.
Thirumukkoodal got its name as three rivers Palar (Ksheera Nadhi), Vegavathi (Saraswathi) and Cheyyar (Bahu Nadhi) merge together at this place. This place is called Triveni Sangamam and is considered equivalent to Ganges. Taking bath here is considered as holy as bathing in Prayag. 
The temple is beautifully located on the banks of the river giving a scenic view. The compound of the temple is just on the shore of the river is a wonderful site to see. Sri Lakshmi Narasimhar temple is located in Pazhaya Seevaram on one side of the river and Sri Appan Prasanna Venkatesa Perumal temple on the other bank of the river.
This temple is said to be 1200 years old, as the oldest inscription found in this temple belongs to 9th Century. This temple is said to have built by a king ruling Thondai Mandalam (with capital as Kanchipuram), by name Raja Thondaimaan Chakravarthy.
According to the legend, the king Thondaimaan once started to Thirupathi to have dharshan of Lord Venkatesa Perumal. He then heard a divine voice telling him that it was not the time to visit Thirupathi as a king from a neighbouring country was nearing his kingdom to wage a war. The voice advised him to be with his son during war time to save the country and later to visit Thirupathi. On hearing this Thondaiman prayed to Lord Venkatesa Perumal and the Lord blessed him to win the battle and gifted him with His Sanku (Conch) and Chakra (Wheel). Thondaiman successfully won the battle and on his way back both the weapons Sanku and Chakra vanished. Later, the Lord directed Sri Ramanujar to install Sanku & Chakra for Him at this place. That’s how the deity here had got Sanku & Chakra here. Then the king Thondaiman surrendered to Perumal at Thirupathi seeking ‘Moksha’. The Lord directed him to come to Thirumukkudal to grant Moksha to him. The king visited here to have dharshan of the Lord. Till then, the Lord here was said to be in ‘Sayana Kolam’ (reclining posture like Ranganathar). When the king visited here the Lord is said to have changed his posture and gave him dharshan in standing posture.
This temple is protected and maintained by ASI. Lots of stone inscriptions are found along all the walls of the temple. These epigraphs belong to various periods starting Raja Raja Chola 1, Rajendra Chola and others. The inscriptions tell a lot about the grants made by various kings to the temple where the temple enjoyed huge popularity.
Interestingly the inscriptions also reveal clearly in detail about the number of students enrolled in college, the number of teachers appointed for each subject and the remuneration paid to them. Also there has been a hostel for this college where the students stayed during their studies and the details of the servants and cooks appointed to take care of the inmates have been detailed in the inscriptions. There has also been a medical centre (Athura Saalai) attached to this college at this place where the students, teachers and the temple staff were treated for various illnesses. This 15 bedded hospital was named after the king ‘Veera Chozhan’ and had ample manpower comprising a physician by name ‘Kodhandaraman Aswathaaman Bhattan’, a surgeon who performed operations, nurses to attend to patients and servants to bring herbs from places and even a barber. The information on the salaries paid to the employees of the hospital and the names of about 20 different types of medicines which were stored in the hospital are well detailed in the inscriptions. There was also a provision made for the reciting of ‘Thiruvaimozhi’ at this temple during Chola period.
Source: Divya darisanam
Adiyen, Baktharkkadiyen, had the rare opportunity of worshiping Lord Appan
Sri Venkatesa Perumal at Thirumukkoodal today. It was also adiyen’s fortune that while adiyen was before the feet of the Lord, His holiness
Sri Vijayendra Saraswathi, visited the temple and worshiped Lord Appan. It
was a rare opportunity that will ever be in my mind during the rest of my life. This ancient temple needs a lot more care and support from both devotees and the government. Jai Shriman Narayan! Saturday 12,2013