Haripad Subramanya Swamy temple, a popular one in Kerala.

 Haripad Subramanya swamy temple.blessingsonthenet.com
The Sree Subrahmanya Swamy temple in Haripad, Alappuzha District   besides being  famous is one of the oldest Hindu places of worship in Kerala. Also known  as Dakshina Palani (Southern Palani), it is believed,  this temple is of great antiquity once worshipped by Parasurama. This suggests temple's origin before the advent of Kaliyuga.
Sree Subrahmanya Swamy temple in Haripad/en.wikipedia.org/
For unknown reasons, Parasurama left the idol of Subramanya in the backwaters of Kandanalloor    - Govindamuttom Backwaters from which it was recovered after the landlords  of Eakachakra (the then Haripad) at the same time had a  dream regarding this idol. The idol  that was  in Kayamkulam lake  was  taken out  at Nelpurakadavu as the villagers suspected  divinity in that idol.
Subrahmanya Swami's Aarattu 2016 festival. YouTube

According to the legend as there was not a permanent shelter built for the idol, it was kept under a banyan tree in a place owned by a Christian family. An half hour worship was done for the deity here and the place where the idol of Subramanya was kept for brief worship,  there is a small temple  in the village  called  (half an hour) Ara Nazhika Ambalam”.

Consecration was done, it is believed, by Lord Vishnu himself disguising as a holy Saint on the Pushya star of Makara Masa and this day is celebrated  annually as  the founding day of the temple. In Malayalam year 1096 the temple  had a fire mishap and fortunately the golden flag mast and the Koothambalam  were not affected.  Maharajah Sree Chithira Thirunal Rama Varma rebuilt the temple and the golden flag mast was re-installed.

The giant 8 foot tall presiding deity Murugan facing east  has four arms carrying Vel (spear) in one hand, Vajrayudha in another hand one hand bestowing blessing (showing Abhahya mudra) and the other toughing the thighs. The idol  is believed be an embodiment (an hamsam of) of Vishnu, Shiva and Brahma all in one form. The temple has four towers - gopuras and the Srikovil (sanctum) is round in shape. Here Murugan's mount Mayil (peacock) is kept in a separate place. There is a Koothambalam within the compound.  On festival days it is used for performing the tradtional dances of Kerala.  The golden flags staff (Dwajasthambam) is the biggest one in Kerala.

After  Thiruvonam, in commemoration of retrieval of the idol Vigraha Labdhi Jalolsavam is conducted in Payippad river for three days. This event attracts a lot of devotees.   Chitira Ulsavam,  Markazhi Ulsavam
Aavani Ulsavam, Thaipooyam  are important festivals here.