Arunachaleshwar Temple, Thiruvannamalai
Why this is the Fire (Agni / Tejas) sthalam
Brahma and Vishnu argued over supremacy; Shiva appeared as a pillar of infinite fire (Linga Purana). Vishnu went down as Varaha, Brahma flew up as a swan — neither could find the ends. Shiva manifested as Arunachala hill. The hill is the cosmic fire-lingam.
The Lingam
Agni Lingam — the entire Arunachala hill itself is the lingam (swayambhu)
Signature ritual
Girivalam — barefoot pradakshina of the 14 km Arunachala hill on every full moon night (1 lakh+ pilgrims). Karthikai Deepam — massive flame lit atop the hill seen for 35 km.
Major festival
Karthikai Deepam (Nov-Dec, Krittika nakshatra of Karthika month), Maha Shivaratri, Pankuni Uthiram
Significance
Ramana Maharshi spent 54 years at this hill (1896-1950). Karthikai Deepam attracts 3 million+ pilgrims annually. Arunachala considered the most spiritually powerful hill in South India per Skanda Purana.