''Karthigai Brahmotsavam'', 2019 at Tiruvannamalai Sri Arunachaleswarer temple, Tamil Nadu

Arunalchaleswarar temple, TN  holidify.com
Arunalchaleswarar temple, TN/arunachalagrace.blogspot.com
Among the Hindu temple festivals of Tamil Nadu,  Karthigai Deepam (Karthigai Brahmotsavam) that falls on the 10th of December this year  is the most important one at temples dedicated to God Shiva.  It is held in the Tamil month of  Karthigai (mid-Nov to mid-Dec) - in the star Krittika or Kirthigai.  No other Shiva temple celebrates this festival on a grand scale with significant religious fervor  as at the Arunachaleswara temple at Tiruvannamalai, a pancha bootha's sthalam where Lord Shiva represents ''Agni'' (fire).
Arunalchaleswarar temple, Tituvannamalai, TN srinithyakalyani.org
Here at this temple town, it is a 10-day event  packed with many rituals and each day  the festival is celebrated with passion and utter devotion. During the long festival period  more than a million devotees  from Tamil Nadu and other adjacent  states visit this famous temple to get the Lord's blessings and participate on a long barefoot walk
clock-wise  around the holy hill of Arunachala - what is called ''Girivalam''- a strenuous religious undertaking with clean mind, body and heart.  Lighting of oil lamps forms an integral ritual of this popular festival that is also celebrated across India, particularly in South India. it is more popular.  Lighting of oil lamps is the fore most important  ritual that has  spiritual connotation  on this day. It is symbolic of getting rid of ego and arrogance, and inviting positive elements  for our well being. The oil lamp symbolizes this spiritual revelation. The wick in the lamp represents our ego, oil in the lamp  our inborn nature that nurtures the ego (the root cause of our miseries); the flame symbolizes  the spiritual wisdom that will do away with  ego (wick) and consumes the innate unwanted behavior (oil). Thus Karthigai Deepam - the lighting of the oil lamps is symbolic of  the victory of good over the  evil, dispelling darkness  and bringing in rays of light - positive elements that help  us  progress in our arduous  lives.  This is the reason why at Hindu households on Karthigai Deepam day, people light up lamps inside and outside the house  to welcome  prosperity, sanctity  and humility in  their lives,  getting rid of  negative elements  and dark  forces that stand as a road block in our progress.
Arunalchaleswarar temple, TN thiruvannamalai.i
Tiruvannamalai, TN, Girivalam map. lijindileep.com
The ten-day ''Deepam'' celebrations at Tiruvannamalai are as follows:

1st Day – Marks flag hoisting on the temple flag-pole  heralding the  commencement of the grand festival at the temple.  Known as Dwajaroghanam, on this day, the presiding deity (utchavar) Lord Arunachaleswara is taken on a silver vahana (mount) in  a procession, in the morning and night. Also taken out on different vahanas in the procession after Deeparadhana (displaying agni before the deities) are five murthis (idols) called Panchamurthigal (in Tamil) such as  Lord Arunachaleswara, goddess Parvati  god Ganesha, god Muruga and god  Chandigeswarar (an integral part of  Shiva temples of Tamil Nadu) 

2nd Day– Markes the procession of five murthis (idols)  on Indira Vimanam (mount of Indira).

3rd Day – The third day event assumes importance at night  with the Panchamurthis  (5 idols mentioned above) taken in a procession on the Simha Vahana (mount of lion).

4th Day – Marks the Kamadhenu Vahanam (mount  of  wish-fulfilling holy cow Kamadhenu) and the all five idols are taken out  along with the wish-fulfilling tree – Karpavruksha (placed on the side of the lord) .

5th Day –Rishaba Vahanam is the major event and the idols are mounted on the huge  silver Rishaba Vahanam (chariot is 25 feet tall). A unique feature is a giant  umbrella of about 17 feet in diameter is also carried along during the procession.
6th Day – The nightly procession includes  five idols in a  nicely carved   silver plated chariot  which is an awe-inspiring vision.

7th Day – The main event is  ‘Maha Ratham, a beautifully carved big wooden chariot  and all the five idols are taken out in a procession  around the four Mada streets. The chariot is pulled by a large number of people.  The big ratha is so wide it almost covers the entire width of the road. 

8th  Day – Marks the Kuthirai vahana (the mount is horse). The fascinating sight is all the legs of  the  horse are off the base not touching it.

9th  Day – The five deities -utchavars are mounted on the Kailasa Vahana (mount  of heaven) and  are taken out at night in a procession all around the Mada street close to the temple, often accompanied by playing of Nadaswaram, drums, fanfare, etc as on other festive days.  

10th  Day – The final day is the most important one and marks the end of the long-drawn festival - Karthigai Deepam. The festival begins in the early morning  around 4 am and a huge oil lamp called   Bharani Deepam is lit  reverentially in the temple in the midst of chanting of mantras by the priests. In the same evening atop the hill of Arunachala at 6 pm, the Maha Deepam (huge oil  lamp) is lit  which is visible at far off distance . In this temple town and across Tamil Nadu in all Hindu households and Shiva and other temples oil lamp is lit with devotion. The belief has been that Lord Shiva who is sn embodiment of Agni (fire) in this temple at Tiruvannamalai  blesses the people for their peace of mind and welfare. Here, at the temple Shiva is referred to as Lord Arunachaleswara.The legend has it Shiva appeared as a huge column of fire whose crown and  bottom can not be fathomed.  Hence, according to the core of  Hindu philosophy  ''God has neither beginning (Aathi) nor end (Antham);  he is formless and is present in Pancha boothas'' (five elements that sustain life on the earth). Therefore, He is omnipresent and omnipotent

The procession of Lord Periyanayagar on Rishaba Vahana (gold plated  bull mount), is billed as a great event. In the float festival Lord Chandrasekarar, Goddess Parvati  and Lord Subramaniar are taken in a boat called ‘Theppam’ in the holy tank. The float festival will be for three days, Lord Arunachaleswara is taken out in a procession around the hill, which is known as Girivalam or pradhakshina. Karthigai Deepam festival at this temple is a great annual event and many VIPs attend this grand function on the final day.  The government makes elaborate security arrangements and travel restrictions close to the temple premises. The state government makes a few hundred buses available to ply the devotees  to the temple town and back.
Tiruvannamalai location map, TN prokerala.com
Worshiping Lord Shiva and god Muruga (Karthikaya) on Karthigai Deepam day  is significant: It symbolizes removal of darkness, bestowing  peace of mind, happiness, infusing positivity in us. Most importantly it enhances our confidence and gets rid of pride, presumption and ego that will retard our life's journey.