The arrangement of the Asta Lingams around the octagonal perimeter of Arunachala reflects the geometry of a Cosmogram. The octagonal shape is surrounded by a total of eight Lingam Shrines (Asta Lingams). Each of these Shrines are located at the four cardinal and four inter-cardinal points. This was also believed by the ancients who originally constructed the Lingams at their eight cardinal and inter-cardinal points to represent, characterise and vitalise certain aspects and qualities of life in relation to specific fields of energy and influence.

The guardians of the four cardinal directions are called the Lokapalas and are the deities who rule the specific directions of space. The name for the eight deities, four of the cardinal and four of the inter-cardinal directions is 'Asta-Dikpalas.’

Asta Lingams:
Indra Lingam (East)
Agni Lingam (South East)
Yama Lingam (South)
Niruthi Lingam (South West)
Varuna Lingam (West)
Vayu Lingam (North West)
Kubera Lingam (North)
Esanya Lingam (North East)

The Lingams have the dominant Navagraha of the God to whom they are associated. It is believed that placating a specific Lingam will bring various benefits that are associated with the respective Navagraha.

As well as the Asta Lingams, there are two additional Lingams on the girivalam roadway which according to the oral tradition of the region are part of what is considered the “Dasa Lingams” (10 lingams) of Arunachala.

Those two additional Lingams are Surya Lingam and Chandra Lingam.

Surya-Arunachala Mythology
There is a vast amount of mythology in connection with Lord Surya at Arunachala which may be found in the: Arunachala Grace Blog  To view a specific post of the Surya-Arunachala mythology, go to this link here.

Its interesting to note the juxtaposition of the Surya and Chandra Lingams in the above map of the Shrines compared to the below layout diagram of Arunachaleswarar Temple’s Moolasthanam, where the lingams are located next to Pradosha Nandi at the entrance of the inner shrine.

Oral tradition reports that the similarity of the juxtaposition of Surya and Chandra Lingams at the gateway of the Lingam of Arunachala Hill and the Shiva Lingam at Arunachaleswarar Temple’s Moolasthanam, was intentional.
 Surya and Chandra Lingams at gateway of Shiva Moolasthanam

Lord Surya
Surya, the Sun, is God incarnate in solar form, a glorious, shining golden orb visible every day. He is Astamurthi, one of the eight forms of Shiva. The Sun alone is the pivot of the entire Universe, the dispeller of darkness, and root cause of the three worlds. He is the deity of great brilliance and is considered the Supreme Soul. There are many names of Lord Surya and each name refers to a particular quality of consciousness—Aditya, Savita, Surya, Mihira, Arka, Prabhakara, Martanda, Bhaskara, Bhanu, Chitrabhanu, Divakara and Ravi.

Surya is the chief of the Navagrahas and is often depicted riding a chariot harnessed by seven horses which represent seven solar rays, seven chakras of the body and seven days of the week.

Lord Surya on his Chariot

Surya's sons, Shani and Yama are responsible for the judgment of human life. Shani provides the results of one's deeds during life through appropriate punishments and rewards while Yama grants the results of one's deeds after death.

In Vedic astrology Surya is considered a malefic on account of His hot, dry nature. Surya represents soul, will-power, fame, the eyes, general vitality, courage, kingship, father, authority figures, benevolence, generosity, grandeur, dignity and friendliness.

Surya has the following associations:

Animals: Deer, Tiger, Lion
Bird: Goose
Gem: Ruby
Metals: Copper and Gold
Direction: East
Food: Wheat
Sign: Leo
Day: Sunday

In Tantra yoga, Surya, the planetary deity of the Sun, represents the Universal male principal, while Chandra, the Moon, represents the Universal female or shakti principle. Surya is also associated with Agni, the god of fire.

Surya Lingam
Darshan of Arunachala from Lingam

Entrance to Surya Lingam

Moopanar Swamigal who was responsible for the restoration of the Asta Lingams at Arunachala was not involved in anyway with restoration work undertaken at the Surya or Chandra Lingams.

Carvings doorway Lingam compound

Surya Lingam in newly renovated compound

Surya Lingam is located after Gautama Ashram and before Varuna Lingam on the left side of the Girivalam Roadway. Including two buildings connected to Shrine priests, the area on which Surya Lingam is situated is less than 1/2 an acre. In 2016 renovation work financed by a family in Chennai, was completed at the Lingam.

Surya Lingam Shrine with Nandi