The sanctum of the temple is set inside the innermost 1st prakara which is a square with about side. This prakara is offset towards the west inside the 2nd prakara, which is also a square with about side. The Shiva sanctum is unusual as it does not have a Shivalinga, rather it has the Chit Sabha (consciousness gathering, also called "chit ambalam") with an image of Shiva Nataraja. This introspective empty space has a curtained space that is 3.5 meter long and 1.5 meter wide. It is called the "rahasya" (secret) in Hindu texts. It consists of two layers, one red, the other black. According to George Michell, this is a symbolism in Hinduism of "enlightenment inside, illusion outside". It is replaced on the tenth day of the main festivals. The Chidambaram Rahasya is the "formless" representation of Shiva as the metaphysical Brahman in Hinduism, sometimes explained as "akasha linga" and divine being same as Self (Atman) that is everywhere, in everything, eternally.