This temple is in Kaippattoor, Pathanamthitta district. Lord Mahadeva is the main deity consecrated here. The temple is on the banks of the Achankovil River. The Lord is addressed as Appooppan by the devotees. Legends say that Arjuna and Krishna came here when the Pandavas were living in the forest. Arjuna prepared food and wanted to worship Lord Siva before eating it. He asked where he should perform the worship, and Krishna asked him to do it at his feet, thinking of Lord Mahadeva. Later, this spot became a rock with more the effulgence of Lord Siva. The spot remained neglected for a long time till the effulgence was found and a temple was built there. The temple is made according to the Kerala style of temple architecture. The water used for the ritualistic bathing of the deity falls into the river. The sanctum is rectangular in shape and made of granite rock. It has no roof. The sanctum is attached to the Thidappally or the kitchen. There are many stone lamps attached to the sanctum wall. Chalana Ganapathy, Nagaraja and Nagayakshy are consecrated here. There is a koovalam tree ( Bael tree) near the flagpost, which is believed to be as old as the temple. Sivarathri and Ayilyam in the month of Kanni are important here. The temple is open from 5 to 12 in the morning and 5 to 8 in the evening. When the water rises in the river, rituals are performed at the Thrikovil Padmanabha Swamy temple.