Sri Mahadevar temple in Chengannur is a sprawling temple complex which is one of the oldest and most celebrated temples in Allapuzha district. The sanctum is circular and the base is stone and the upper half of the sanctum is of teak. The conical dome is copper plated. Lord Shiva and Lord Parvati are in many shrines back to back. The devi faces west and the lord faces east. The lingam is a swayambhu lingam and is gold plated. It bears the image of Sri Ardhanareeswara (Shiva-Shakti) aspect.
Sri Parvati unlike the Moolavar images is made of Panchaloham. There is also a shrine for Sri Krishna. This temple was extensively renovated in 18th century after it got damaged by fire. The mandapams exclusively the mukamandapam boast of excellent wood work. The massive three storeyed edifice in the west coast pattern is the gopuram/entrance. The temple is associated with the Daksha yagna. Different parts of the body fell in different places in the sub-continent each of which has become a Shakti Peetam now. Stala purana states that Lord Sati’s loins fell on the spot in Chengannur. The distinguishing feature is the festival of Triputharattu which is a symbol of fertility. The Goddess also has menstrual periods like any other woman, though not as monthly cycles.
The puranas says that the trinity gods bade Sage Agastya to go south to correct the earth’s imbalance as all the divine entities had congregated in the north in the Himalayas for the wedding of Sri Shiva and Lord Parvati. The sage did as he was instructed but however he was sad that he missed the rare opportunity to witches the celestial event. Lord Shiva and Parvati however made amends by appearing before the sage after the wedding. During their trip to the south, Lord Parvati menstruated here and hence remains in this place until the period ended. This place where she menstruated came to be called as Chen Kunnu (Red Hill) which then became Chen Kunnu Ooru (Ooru in town/village) and finally Chengannur.