The Thrichittatt Mahavishnu Temple, Kerala built by one of the Pandava brothers

Trichittatt templ,  Chengannuren, Kerala. wikipedia.org/

Loation map, Onmanorama Travel - Malayala Manorama

The Thrichittatt Mahavishnu Temple (also called Thiruchenkundrur and Imayavarappan temple) located in Chengannur, Alappuzha District, Kerala, South India is  glorified in the Nalayera Divya Prabandha, by Nammalwar, one of the revered Tamil Azhwar  saint- poets  of the 8th century. One of the 108 Divya Desam Shetrams  dedicated to  Sri Krishna, an avatar of Vishnu, who is worshiped as Imayavarappan,  it  is an ancient temple and has links with the legend of Mahabharata. Here, the tradition has it that  the five Pandavas are believed to have built one temple each.

It is one of the five ancient shrines in the Chengannur area of Kerala, connected with the legend of Mahabharata.  According to the legend the Pandava brothers of the great epic Mahabharata, having  crowned Parikshit as king of Hastinapura, had  left on a pilgrimage down south. Mesmerized by the serene and quiet ambiance and the picturesque  surroundings, upon arriving on the banks of the river Pamba, each one of Pandava brothers is believed to have installed a tutelary image of  Sri Krishna, their mentor-god; Thrichittatt Maha Vishnu Temple by Yudhishthira, Puliyur Mahavishnu Temple by Bheema, Aranmula Parthasarathy Temple by Arjuna, Thiruvanvandoor Mahavishnu Temple by Nakula and Thrikodithanam Mahavishnu Temple by Sahadeva.

The sanctum of Trichittatt temple  en.wikipedia.org

Trichittatt templ,  Chengannuren, Kerala. Just Kerala

 When the Mahabharata war was on, Yudhishthira, the eldest of the Pandava brothers, a man of virtue and moral disposition, committed a sin by lying to his Guru Dronacharya to come out victorious. To make amends for committing a deliberate sin, he did  penance, worshiping the lord Imayavar (Devas ) who  had already come to this place prior to Yudhishthira. Hence the deity here is referred to as Imayavarappar.

The great Tamil Azhwar saint  Nammalvar made references to this temple (in circa 800 AD) in his devotional hymns. Stone inscriptions in the temple date it back to the Second Chera Empire (800 - 1102 AD).  The temple was built by Devas, it is believed locally. Despite the temple's antiquity, there are no clear official  records to confirm the date of origin of this ancient place of worship. 

Built in Kerala style architecture, the temple has neither  gateway tower nor covered Prakara path as one will see in many temples of other southern states. Kshetra-Madilluka (rectangular boundary wall) around the temple pierced by the gateways, encloses all the shrines of the temple. The flag post or Dwajasthambam is facing the  sanctum - Srikovil where the main deity is enshrined.  The main shrine and the connected  hall are  located in a rectangular structure called Nallambalam, which has pillared halls and corridors. Chuttuambalam is the outer pavilion within the temple walls The Namaskara mandapa, where the devotees prostrate before the deity,  lies between the entrance of Nallambalam to the sanctum with a raised  square platform  and a pyramidal roof. Thevrapura (similar to Madappalli of Tamil Nadu) is the temple kitchen  where the prasadams - offerings to the deity are reverentially cooked and it is on the left of Namaskara Mandapa from the entrance.  Balithara or Balipetam  is an altar meant for making ritualistic offering to demi-gods and the festive deities. The Srikovil on an elevated platform with a single door  can be accessed through five steps. The Kerala tradition has it that only the main priest called Thantri and the second priest called Melshanthi alone can enter the Sree Kovil. 

The  sanctum has a circular plan with the base built of granite and the overlying superstructure built of laterite  with conical roof made of terracotta tile supported from inside by a wooden structure. Sri Krishna, the main deity has Vishvarupa posture and is 4 foot tall. In the great Mahabharata war Sri Krishna gave Viswaroopa Darshan before Arjuna and gave a pep talk not to deviate from his duty and the path chosen by him. There are other deities in the second precinct such as Sastha, Yakshi, Nagaraja and others. 

Vaikunta Ekadasi and Thiruvonam are the main festivals here After 1957, the festival of Gosala Krishna Temple at Thiruvanvandoor starts  from Thrichittatt  Maha Vishnu temple when 25 caparisoned elephants are taken in a procession  accompanied by music to the Thiruvanvandoor temple.

The temple is being   managed by Travancore Devaswom Board of the Government of Kerala.
 https://en.wikipedia.org/wiki/Thrichittatt_Maha_Vishnu_Temple