Garbhagriha is the main Sanctum of the chief deity of the temple. Although the term is related mainly with Hindu temples, it is also associated with Jain and Buddhist temples. The room has a single entrance, without any windows. It is usually constructed in a spacious manner, in order to be seen by the worshippers outside.
Entrance to the Hindu Garbhagraha is restricted only to priests and other devotees are allowed to sit only outside the sanctum of the temple. The entrance of the Garbhagraha would be covered with the divine guards of the deities on both the sides, who appear in a fierce manner, with weapons on their hands. In Tamil language Garbhagraha is called as karuvarai which means the interior of the sanctum sanctorum.
Whenever if any devotee visits the temples, he / she must compulsorily worship the main deity situated in the Garbhagraha of the temple, in order to get the full grace of the almighty. In some temples, women priests are also allowed to enter inside the sanctum of the temple, and to perform puja to the deities.
Currently, in some temples, non-Brahmin priests are also allowed to enter inside the sanctum of the temple and they are permitted to do puja to the deities. In general, before entering the sanctum of the temples, the mind and body of the priests must be kept clean. The chief deity would be having great powers, and hence purity in body and mind must be strictly maintained by the priests while touching the deities.
We can also consider our puja room as the main shrine of the temple, and perform abhishekham and puja to the idols at our home. We can also chant the Mantras and offer the holy Prasad to the divine deities.