A cella (from Latin for small chamber) or naos (from the Greek for temple), is the inner chamber of a temple in classical architecture.
Greek and Roman temples
In Ancient Greek and Roman temples the cella is a room at the centre of the building, usually containing a statue, or idol, to the particular god venerated by the temple. In addition the cella may contain a table or plinth to receive votive offerings.
The cella is typically a simple, windowless, rectangular room with a door or open entrance in the middle of one of the shorter walls. In larger temples, the cella may be divided into two or three aisles by rows of columns. They may also contain an adyton — an area restricted to access by the high priests.
The temple to Venus built by Hadrian in Rome had two cellae, both enclosed, in a single peristyle.
Ancient Egyptian temples
In the Ptolemaic period of Ancient Egypt the cella referred to that which is hidden and unknown inside the inner sanctum of a temple, existing in complete darkness, meant to symbolize the state of the universe before the act of creation.
Etruscan temples
According to Vitruvius, Etruscan temples had three cellae, side by side.
Christian churches
In early Christian and Byzantine architecture, the cella is an area at the centre of the church reserved for performing the liturgy.
In later periods a small chapel or monk's cell was also called cella.